Abstract: Melt flow rate is an important index for characterizing melt fluidity of thermoplastic and it can guide the processing.Temperature,preheat time(and test starting time),extrudate cut-off time interval,piston starting position and piston displacement are main factors affecting the test results of melt flow rate.Melt flow rate test method standards of ISO and ASTM were compared and analyzed from above affecting factors.It was found that except not setting starting time,ISO was more reasonable than ASTM.Finally,revising suggestions on melt flow rate test method national standard of GB/T 3682-2000 were put forward according to the comparison and analysis results.