The invention relates to a gas mixing controller of a semiconductor device. The gas mixing controller adopts the following technical schemes that the gas mixing controller comprises an input part, a control processing part, an output part, RS485 communication ports and a power supply; the input part comprises an analogue signal collecting module, an oxyhydrogen ratio input module and an SIH4 pressure input module; the output part comprises an analogue channel output module, a control channel output module, an oxyhydrogen ratio protection output module and an SIH4 over-pressure output module; one RS485 communication port is connected with a digital mass flow meter; the other RS485 communication port is connected with an upper computer; the power supply adopts an isolation DC-DC (direct current to direct current) module, and the power supply is converted through the isolation DC-DC module into power supplies required for five loops, namely the gas mass flow meter, the analogue channel chip, a single chip system, a main communication port and a slave communication port. The controller disclosed by the invention can monitor gas flow of different mass flow meters according to control rules and programs which are transmitted by the upper computer for the gases, carries out interlock and protection at the same time, can be suitable for the gas analogue mass flow meter or the digital mass flow meter, can be connected with eight mass flow meters, is especially suitable for the device with gas control of the semiconductor, and is high in intelligence, strong in function, low in cost, high in accuracy, safe and reliable.