Suspending powder in dielectric fluid of EDM (electrical discharge machining) has been developed to improve the quality of machined surface recently. The used powders are usually Al, Cu, Cr and so on metal powder because conductive particle can increase the spark gap and improve surface roughness of machined surface. Semi-conductive powder, Si is also utilized for the sake of increasing machining speed. This paper presents a new tryout to suspend polymer particles in the dielectric fluid of EDM. Experimental results show that the EDM process with suspending polymer particles still can be carried out but its surface roughness is not so good in conventional EDM oil. However the conventional EDM oil was taken the replace of silicone oil, suspending polyaniline (PANI-emer) of high molecular weight (Mw~65000) has finer improvement even better than using Si powder. Its surface roughness achieves less than Ra 0.2μm at low concentration and will be decreased gradually with increasing the concentration of PANI-emer (Mw~65000). The surface roughness is Ra 0.14μm when the powders concentration is 10g/l. Even for different type of polyaniline shows different machining characteristics. The surfaces roughness becomes worse when the concentration of low molecular weight PANI-emer (Mw~20000) is higher. An electric-conductive PANI-salt powder has a rapid decrease of surface roughness with increasing its concentration than other materials.