Abstract: To discuss the effect of pin carding plate on fiber length distribution in the card slivers,length tests to the card slivers under different carding plate gauge,taker-in speed and doffer speed using pin carding plate and saw-tooth carding plate under the card taker-in by USTER AFIS single fiber tester were done.The results show that compared with saw-tooth carding plate,carding action of pin carding plate is more gentle,which is favorable to reducing fiber damage as a whole,especially when the gauge is small.Compared with installing taker-in grid,the taker-in installed carding plate is favorable to improving fiber length distribution in the card sliver as a whole.