Abstract: During post emulsifying penetrant inspection，parameter option of emulsifier concentration and emulsifying time will directly impact on sensitivity level of penetrant detection. The article mainly takes an example of chromium plating and grinding parts and HVOF parts, analyzes emulsifier concentration and emulsifying time impact on penetrant indication and performs instructions and demonstrations. The experiment indicates that we shall strictly control emulsifier concentration and emulsifying time during post emulsifying fluorescent penetrant inspection. If we select emulsifier concentration 15%, emulsifying time 10~15 s after testing many times, it will reach optimum proportioning, make flaw indication clear. Detection sensitivity level will reach the largest.