Abstract: A variable pitch lead transmission mechanism includes a slider, a screw rod having a screw thread and two opposite screw thread surfaces and mounted on the slider, a driver contacting with one of the screw thread surfaces and adapted to be translated by a power source in order to in turn rotate the screw rod, and an elastic element mounted between the screw rod and the driver for providing a buffering action therebetween. Preferably, the buffer effect of the elastic element automatically accommodates the spin angle .beta. of the driving base and the contact locations between the driver and the screw thread surface so as to avoid therebetween an adversely expanded clearance.