The invention discloses a method for expanding a CAN bus interface of a coal mining machine. The method comprises the steps of 1), connecting a CAN bus signal output by the coal mining machine to a CAN to TCP module; 2), converting the CAN bus signal into a TCP signal through the CAN to TCP module; 3), transmitting the converted TCP signal to a protocol conversion module of an upper computer in a wire or wireless transmission mode; 4), converting the received TCP signal by the protocol conversion module into a standard industry protocol which is requested and approved by a third party user. According to the method, an existing coal mining machine is unnecessarily modified, and the CAN bus interface of the coal mining machine can be expanded into the standard industry protocols such as MODBUS-TCP or OPC only by converting the CAN bus signal of the coal mining machine, so that the working state of the coal mining machine can be read and controlled by various configuration software. The method has great significance in the coal mining machines currently used by various coal mines, and other modules cannot be installed in the coal mining machines.