A permanent magnetic lifting device, which has: a housing, at the bottom of which is a clamping surface for clamping objects; a fixed magnet, set in said housing relatively fixed to the housing; a turnable magnet, set in said housing relatively turnable to said fixed magnet; when said turnable magnet is in the first position relative to said fixed magnet, the magnetic force generated by said fixed magnet and said turnable magnet to said clamping surface is zero magnetic force; when said turnable magnet is in the third position relative to said fixed magnet, the magnetic force generated by said fixed magnet and said turnable magnet to said clamping surface is the maximum magnetic force; whereby the permanent magnetic lifting device also has a positioning mechanism for second position which is adapted to position said turnable magnet in the second position relative to said fixed magnet, such that said fixed magnet and said turnable magnet generate trial clamping magnetic force to said clamping surface for clamping objects on trial; the trial clamping magnetic force being higher than zero magnetic force and lower than maximum magnetic force; wherein said fixed magnet and said turnable magnet are both cuboids, said fixed magnet along its height is perpendicular to the plane on which said clamping surface lies, two sides on the width of said fixed magnet are S pole and N pole respectively, two sides on the width of said turnable magnet are S pole and N pole respectively, said turnable magnet is able to turn around its own centerline parallel to its lengthwise direction; when said turnable magnet is turned to said first position, N pole on said turnable magnet and S pole on said fixed magnet are on one side of the width of said fixed magnet, S pole on said turnable magnet and N pole on said fixed magnet are on another side of the width of said fixed magnet; when said turnable magnet is turned to said second position, the center plane of said turnable magnet, which bisects the turnable magnet along its height, makes a predetermined included angle with the center plane of said fixed magnet, which bisects the fixed magnet along its height; when said turnable magnet is turned to said third position, S pole on said turnable magnet and S pole on said fixed magnet are on one side of the width of said fixed magnet, N pole on said turnable magnet and N pole on said fixed magnet are on another side of the width of said fixed magnet; and wherein the permanent magnetic lifting device also has a handle, this handle is for an operator to operate manually outside said housing to drive said turnable magnet to said first position, said second position or said third position; and said positioning mechanism for second position includes a first retaining pin, located in the part of said housing, corresponding to the travel route of said handle, in the course of said handle driving said turnable magnet to turn from said first position to said third position; whereby the positioning mechanism for second position includes a first spring, applying elastic thrust to the first retaining pin so that the first retaining pin protrudes out of the housing in normal state; and an actuator, exposed outside said housing for an operator to operate so that said first retaining pin overcomes the elastic thrust of said first spring and retracts into said housing; and there is a slope on the front end of said first retaining pin, in the course of said handle driving turnable magnet to turn from said first position to said third position, when said handle moves to the position where said first retaining pin is set, under the condition that said actuator is not operated, said handle touches said slope and pushes that slope, so that said first retaining pin overcomes the elastic thrust of said first spring and retracts into said housing, enabling said handle to pass the position where said first retaining pin is set; in the course of said handle driving turnable magnet to turn from said third position to said first position, when said handle moves to the position where said first retaining pin is set, under the condition that said actuator is not operated, said handle touches the plane, which is on the back of said slope, of said first retaining pin and is blocked by that first retaining pin, thus being positioned where said first retaining pin is set; and further the rear end of said first retaining pin touches said first spring, the middle part of said first retaining pin integrates with said actuator, said slope is the inclined plane formed by means of cutting the front end of first retaining pin intersecting the axis of said first retaining pin.