The experimental analysis on the influence of duty factor and powder particle size on discharge energy, material removal rate and surface integrity is made during powder mixed electrical discharge machining process. Molybdenum-di-sulfide (MoS2) powder particles of two different size viz. 40μm (micro) and 90 nm (nano) are used. During experimentation duty factor is varied as 2, 4, 6, 8, 10 and 12. A comparative evaluation on the effect of using two size of molybdenum-di-sulfide powder particle in dielectric medium is studied. For all duty factors, micro powder offered high discharge energy and better surface finish compared to that of nano powder. Nano powder offered high material removal rate compared to that of micro powder. The occurrence of series discharge during powder mixed electrical discharge machining is observed using pulse train generated in gap and using scanning electron microscope image of machined surface. The e energy dispersive X-ray spectroscopy analysis of machined surface reveals the deposition of molybdenum-di-sulphide from dielectric medium for both micro and nano powder mixed electrical discharge machining process. © Published under licence by IOP Publishing Ltd.