The invention relates to a transmission extension rod for a power tool. The transmission extension rod for a power tool is used for connecting a main clamp and a working head of the power tool, and comprises an outer sleeve, a shaft bush, a transmission shaft, a front protecting cover set and a multi-way positioning device, wherein the outer sleeve is used for combining with the power tool, and the main clamp is positioned in the outer sleeve, and a plurality of through holes which are accommodated with a positioning component respectively are formed on the outer peripheral surface of the outer sleeve; one end of the shaft bush is rotatably connected to the outer sleeve, and at least one positioning hole is formed on the outer peripheral surface of the shaft bush; the transmission shaft is inserted in the shaft bush, and one end of the transmission shaft is connected to the main clamp, while the other end is connected to an auxiliary clamp so as to ensure that the auxiliary clamp clamps the working head to rotate; the front protecting cover set is used for fixing an automatic feeding device at the front end of the shaft bush, and the automatic feeding device can be rotated along the shaft bush; and the multi-way positioning device is used for pressing positioning components so as to ensure that the positioning components are fixedly embedded in the positioning holes to lock the shaft bush.