A single axle bidirectional symmetry stretch testing machine belongs to the experimental mechanics equipment technology field, including: the step-by-steps motor 11, the step-by-steps motor controller, the strength sensor, the wormwheel, the worm, the ball bearing screw mandre, the left nut, the right nut, the linear slideway, the axletree, the base 1, the shaft coupling, the testing sample holding device; the step-by-steps motor connects with the worms by the shaft coupling; the wormwheel cooperates with the worm, the linear slideway and the axletree locates on the base; the strength sensor fixes on the right nut of the ball bearing screw mandrel, spreads the one side of the testing sample holding device, the other side of the testing sample holding device fixes on the left nut. The invention is: uses the machine transmission to improve the transmitting precision; uses the step-by-steps motor to load; the distortion measure can use the step-by-steps motor to compute or uses the non-touch photics displacement measure system.