Based on gas explosion caused by unstable gas density, intelligent detecting and ventilation systems of gas concentration with FPGA controller were put forward. Researchers were hard to design a accurate mathematical modeling according to irregular law of gas concentration, FPGA chip was used as hardware design in this system, which realized fuzzy PID controller without accurate model ling. Running speed and stability of FPGA was better than single chip and it had better instantaneity, which could test gas concentration instantly to control economic operation of ventilator. This design not only decreased incident race but also improved waste of power energy.