In order to realize a Long-wave Infrared (LWIR) optical wireless communication, a long-wave infrared optical wireless communication system model based on pulse width modulation was estabished, the performance of this system was analyzed, and an expression of bit error rate was proposed. An experimental system was designed, the change of average output optical power of CO2 laser was analyzed, the average of received laser pulse width and random variation of pulse width affected by the noise under different duty ratios were analyzed. The relationship between the average of output optical power and pulse width with duty ratio was obtained, and the distribution law of pulse width was also obtained, and then the experimental results and theory analysis results were compared, based on this, the optimal judgment threshold of pulse width and the relationship between system working parameters with (Bit Error Rate)BER were obtained. It is proved that a long-wave infrared optical wireless communication can be achieved based on CO2 laser by the pulse width modulation.