PU fiber is getting more and more active in the market. However, there are sometimes biggish deviations on PU fiber content in the end products tested by different methods or institutions, which could always bring about some dissension. This paper has carried out detailed quantitative and qualitative analysis on how to reduce the deviation of PU fiber content by splitting method and chemical method according to a battery tests. It is proved that samples should be treated beforehand to limit the testing D-value under the relative testing conditions.