A driving mechanism for fastener driving machine, including a rotatable crank; a driving rack element rotatably installed on the crank, which comprises an engaging element, a support element and a driving rack; at least one fixed guide element. The support element and/or engaging element can move along the set trajectory. The present invention has a simple structure, a few parts and stable operation. When the crank rotates, the motion trajectory of the engaging element is straight or approximately O°, so as to reduce the kinetic friction force of load to the maximum extent, preventing wear problem, and guaranteeing constant direction of thrust on the impact unit in the course of compressed energy storage and low eccentric load in late stage, the quick release of driving mechanism is implemented, the operational stability and smoothness of impact unit are guaranteed, the work quality is upgraded.