In this paper we discuss the temperature dependence and its effect on surface roughness. In abrasive flow machining (AFM) process the temperature of media rises drastically due to procedure of being sheared. To examine the effect of media temperature on surface roughness, an experiment system with the functions of controlling, measuring and recording temperature is set up. The variable trend of media temperature is revealed during AFM. Experiments are performed at different temperatures. Experimental results show that the media at high temperature results in less improvement in surface roughness. Therefore the media can have good machining performance in the first few cycles and the media temperature rise rapidly. Finally we conclude that the best workable temperature should be below 25 °C during the AFM.