A PLC programming auxiliary system and a method thereof are provided. The system comprises: a web server providing a complex algorithm for programming PLC, correctness checking of the programming and user logic compilation functions; a plurality of client computers connecting with a web server and the programmed PLC devices via a network link. When a client computer is linked to the website server by a user, a web browser on the client computer requests from the web server to download client programming software for programming an appropriate PLC device, and the client programming software for programming the appropriate PLC device is executed within the web browser on the client computer, to enable the client computer to configure the PLC device and program the user logic through the client programming software for programming the appropriate PLC device, and the client computer implements an interface connection and an interaction operation of the web server with the user through the client programming software for programming the appropriate PLC device.