The invention relates to a special device for testing, in particular to a special device for handcart circuit breaker mechanical feature testing and belongs to the handcart circuit breaker device technical field. The special device includes an auxiliary function box, a special adapter plug and a circuit breaker mechanical feature tester; a switching-off signal input socket is connected with a switching-off socket of the mechanical feature tester through a wire; a switching-on signal input socket is connected with a switching-on socket of the mechanical feature tester through a wire; an energy storage power source input socket is connected with a spring energy storage power source output socket of the auxiliary function box through a wire; and an unlocking power source input socket is connected with an electric unlocking power source output socket of the auxiliary function box through a wire. The special device of the invention has the advantages of convenient operation and high practicability. With the special device adopted, complicated and inefficient manual wiring and energy storage and a dangerous unlocking step can be avoided, and the accuracy, safety and efficiency of testing work can be greatly improved.