A non-intrusive design of self-checking finite state machines (FSMs) in VLSI circuits was investigated using convolutional codes. We propose a novel scheme which cannot only detect but also correct errors occurred in FSM states. The error state will be corrected and sent back to the FSM, so that the concurrent error in the current state is detected and corrected immediately. Moreover, we realize the IP core of the self-checking module by SMIC 0.25-um CMOS technology and also simulate its function in FPGA.