A rail clamping device for a trapped rail vechicle, comprising a fixed seat, a slide seat and clamping members, the slide seat is connected to the fixed seat in a sliding manner and forms a transverse moving pair with the fixed seat; a steel rail on which the trapped rail vehicle runs comprises a rail head, a rail web and a rail bottom, and a cross section of the steel rail is of an I shape; the clamping members comprise outer clamping members and inner clamping members; and an appearance of a lower portion of the inner clamping members is a straight cylinder, a bottom end of a lower portion of the outer clamping members is provided with a flange, or a bottom end of a lower portion of the inner clamping members is provided with a flange, and an appearance of a lower portion of the outer clamping members is a straight cylinder, characterized in that a bottom of the fixed seat is recessed to form a guide groove, and a top of the slide seat is bulged to form a slide block; and the fixed seat and the slide seat are mutually nested to form the moving pair through the guide groove and the slide block; the outer clamping member and the inner clamping member form a rail clamping cavity with a bottom of the slide seat; and the cavity is used for accommodating the rail head; the outer clamping members and the inner clamping members are respectively disposed at two sides of the steel rail, so that the inner sides of the clamping members limit the left side and the right side of the rail head; the slide seat is fixedly connected with the clamping members; and in one clamping member, a distance between one outer clamping member and one inner clamping member is fixed; the inner clamping member comprises an inner clamping wheel shaft and inner clamping wheels; the inner clamping wheel shaft partially protrudes out of the inner clamping wheels, and an upper portion of the inner clamping wheel shaft is fixedly connected with the slide seat so as to be movably connected with the inner clamping wheels; and the inner clamping wheel is of a straight cylindrical shape; the outer clamping member comprises an outer clamping wheel shaft and outer clamping wheels; the outer clamping wheel shaft partially protrudes out of the outer clamping wheels, and an upper portion of the outer clamping wheel shaft is fixedly connected with the slide seat so as to be movably connected with the outer clamping wheels; and the upper portion of the outer clamping wheel is of a straight cylindrical shape, a lower portion of the outer clamping wheel downward extends to enable the rail web to partially stretch into the rail clamping cavity, and the bottom end of the outer clamping wheel extends towards the direction of the rail web to form a flange, and the flange stretches into a groove corresponding to the rail web on the steel rail, so that the flange is capable to limit a bottom side of the rail head. a steel rail on which the trapped rail vehicle runs comprises a rail head, a rail web and a rail bottom, and a cross section of the steel rail is of an I shape; the clamping members comprise outer clamping members and inner clamping members; and an appearance of a lower portion of the inner clamping members is a straight cylinder, a bottom end of a lower portion of the outer clamping members is provided with a flange, or a bottom end of a lower portion of the inner clamping members is provided with a flange, and an appearance of a lower portion of the outer clamping members is a straight cylinder, characterized in that a bottom of the fixed seat is recessed to form a guide groove, and a top of the slide seat is bulged to form a slide block; and the fixed seat and the slide seat are mutually nested to form the moving pair through the guide groove and the slide block; the outer clamping member and the inner clamping member form a rail clamping cavity with a bottom of the slide seat; and the cavity is used for accommodating the rail head; the outer clamping members and the inner clamping members are respectively disposed at two sides of the steel rail, so that the inner sides of the clamping members limit the left side and the right side of the rail head; the slide seat is fixedly connected with the clamping members; and in one clamping member, a distance between one outer clamping member and one inner clamping member is fixed; the inner clamping member comprises an inner clamping wheel shaft and inner clamping wheels; the inner clamping wheel shaft partially protrudes out of the inner clamping wheels, and an upper portion of the inner clamping wheel shaft is fixedly connected with the slide seat so as to be movably connected with the inner clamping wheels; and the inner clamping wheel is of a straight cylindrical shape; the outer clamping member comprises an outer clamping wheel shaft and outer clamping wheels; the outer clamping wheel shaft partially protrudes out of the outer clamping wheels, and an upper portion of the outer clamping wheel shaft is fixedly connected with the slide seat so as to be movably connected with the outer clamping wheels; and the upper portion of the outer clamping wheel is of a straight cylindrical shape, a lower portion of the outer clamping wheel downward extends to enable the rail web to partially stretch into the rail clamping cavity, and the bottom end of the outer clamping wheel extends towards the direction of the rail web to form a flange, and the flange stretches into a groove corresponding to the rail web on the steel rail, so that the flange is capable to limit a bottom side of the rail head.