A manual dual-power supply transfer switch, the switch comprising: a four-bar linkage, a first movable contact, a second movable contact, a first power terminal electrically connected with the first power supply, a second power terminal electrically connected with the second power supply, a first load static contact and a second load static contact, wherein the movement of the four-bar linkage acts on the first movable contact and the second movable contact at the same time, so that the manual dual-power transfer switch can be switched among the following states: a state in which the first power supply is closed, wherein only the first movable contact is connected between the first power supply terminal and the first load stationary contact; a state in which the second power supply is closed, wherein only the second movable contact is connected between the second power supply terminal and the second load stationary contact; and a dual-open state in which the first movable contact is not connected between the first power terminal and the first load static contact and the second movable contact is not connected between the second power terminal and the second load static contact, characterized in that the four-bar linkage comprises a switch handle, a cam and a connecting rod connected between the switch handle and the cam, one end of the connecting rod is eccentrically connected to the switch handle relative to a handle axis, the other end of the connecting rod is eccentrically connected to the cam relative to a cam axis, an outer contour of the cam has a portion of a first radius of curvature and a portion of a second radius of curvature, the cam is configured to drive the first movable contact and the second movable contact with the portion of the second radius of curvature; and the second radius of curvature is larger than the first radius of curvature. a four-bar linkage, a first movable contact, a second movable contact, a first power terminal electrically connected with the first power supply, a second power terminal electrically connected with the second power supply, a first load static contact and a second load static contact, wherein the movement of the four-bar linkage acts on the first movable contact and the second movable contact at the same time, so that the manual dual-power transfer switch can be switched among the following states: a state in which the first power supply is closed, wherein only the first movable contact is connected between the first power supply terminal and the first load stationary contact; a state in which the second power supply is closed, wherein only the second movable contact is connected between the second power supply terminal and the second load stationary contact; and a dual-open state in which the first movable contact is not connected between the first power terminal and the first load static contact and the second movable contact is not connected between the second power terminal and the second load static contact, characterized in that the four-bar linkage comprises a switch handle, a cam and a connecting rod connected between the switch handle and the cam, one end of the connecting rod is eccentrically connected to the switch handle relative to a handle axis, the other end of the connecting rod is eccentrically connected to the cam relative to a cam axis, an outer contour of the cam has a portion of a first radius of curvature and a portion of a second radius of curvature, the cam is configured to drive the first movable contact and the second movable contact with the portion of the second radius of curvature; and the second radius of curvature is larger than the first radius of curvature. a state in which the first power supply is closed, wherein only the first movable contact is connected between the first power supply terminal and the first load stationary contact; a state in which the second power supply is closed, wherein only the second movable contact is connected between the second power supply terminal and the second load stationary contact; and a dual-open state in which the first movable contact is not connected between the first power terminal and the first load static contact and the second movable contact is not connected between the second power terminal and the second load static contact, characterized in that the four-bar linkage comprises a switch handle, a cam and a connecting rod connected between the switch handle and the cam, one end of the connecting rod is eccentrically connected to the switch handle relative to a handle axis, the other end of the connecting rod is eccentrically connected to the cam relative to a cam axis, an outer contour of the cam has a portion of a first radius of curvature and a portion of a second radius of curvature, the cam is configured to drive the first movable contact and the second movable contact with the portion of the second radius of curvature; and the second radius of curvature is larger than the first radius of curvature.