Abstract: A rapid replacing structure for multi-purpose saw includes an operating mechanism, a clamping mechanism and a collet. The collet is released or clamped by driving the clamping mechanism through the operating mechanism. The structure includes an output shaft having top and bottom openings and defining a chamber. The collet is mounted in the chamber. The clamping mechanism includes a spring, a collet sleeve, and a compressor arm. The collet sleeve is disposed around and movable along an upper portion of the collet. One end of the spring contacts with the bottom wall of the output shaft, while another end contacts with the collet sleeve. The compressor arm includes a top lever, and a top ring integrally formed on a lower end of the top lever and located above the collet sleeve. The top lever of the compressor arm is connected in a contacted manner to the operating mechanism.