By using time and space-resolved luminescence technique,the expansionary behaviour plasma in silane and methane mixed gas by pulsed TEA CO2 laser is studied.In the area of laser focus,the character of light emission frome plasma which depends on space position and experiment parameters is obtained.The results show that laser induced breacdown producing a detonation wave and then expanding in a simlary manner to blast wave is the basic dynamic process of this plasma.In addition,the relation between chemical reaction and explosion wave of plasma is analysed.