The invention relates to a constant-force hanging bracket box body tension testing device. The device is characterized by comprising a testing platform (1) and a constant-force hanging bracket box body tension testing tool installed on the testing platform (1). The constant-force hanging bracket box body tension testing tool comprises a first counter-force base (3), a second counter-force base (4), a jack base plate (5), a double-acting hollow jack (6), a jack pull rod (7), a force sensor flange plate (8), a force sensor (9), a force sensor lengthening rod (10), a first adjusting screw rod (11), a grating ruler connecting plate (12), a grating ruler (13), a second adjusting screw rod (14) and a connecting base plate (15). The second adjusting screw rod (14) is just located on the right of the first adjusting screw rod (11). The constant-force hanging bracket box body tension testing device and a constant-force hanging bracket box body tension testing method have the advantages of being capable of completely simulating the actual using state of a constant-force hanging bracket box body and capable of objectively verifying the design of the constant-force hanging bracket box body.