Abstract: In this paper the mechanism of high frequency short pulse electrochemical machining （HSPECM） is investigated．The results show that the intensive pulse effects by HSPECM improve the behaviour of the inter-electrode gap of electrochemical machining （ECM）．The intensive pressure wave the large inverse current in pulse interval and microsparks all result in intensive depolarisation so the current efficiency feature is improved and the cut-off gap is shortened．These lead to intensive anodic dissolution localisation ability and micro inter-electrode gap machining．It has been proved by technology experiments that the above alternations result in high machining accuracy better surface quality and good profit．For example in die-sinking samples by HSPECM ellipticity attains to0．02mm  repeatability to0．05mm‚surface roughness to Ra0．60μm．It improves ECM from sem-i rough ma chining to precision machining． 

Key words: high frequency short pulse current, electrochemical machining, precision machining