With regard to the plug-and-play problems of the uncertain number of slave stations on RS485 bus,taking the detection requirements of photoelectric modules as an example,a plug-and-play software control method of RS485 bus based on the unique identifier of single chip microcomputer equipment is proposed in the paper.Without changing the hardware circuit,through this method,functions including scanning the number of slave stations,automatically distributing the addresses of slave stations and hot plug detecting for slave stations in the RS485 buses can all be realized.In addition,the effectiveness and flexibility of this method can be proved by experimental data,which solves the problems of user’s demand for arbitrary plugging of the slave stations.