Shuo Wen Guang Yi has had great achievements in function words explaining,but there still existed many defects. By using the research achievements of the ancient writing,grammar and lexicology,the explaining defects of the function words in Shuo Wen Guang Yi could be found in the following two aspects.First,the errors existed in explaining including the errors followed Shuo Wen Guang Yi and the errors existed in the interpretation itself.Second,the explaining is farfetched,including the interpretation of the v...