Abstract:In 1989-1993, systematic observations on 1st-3rd generation of Ancylis sativa Liu were carried out in Taigu County,Shanxi Province. Based on those investigatory data, 15 natural population life table,one average life table of 1st-3rd generations in five years were developed. The results showed as follows:1. The eggs and 1st-2nd instar larvae of 1st generation are a weak link of the life history and the generation;2. The trend index of population of 1st-2nd, 2nd-3rd and 3rd to next 1st generations were 2.45, 2.7 and 0.21, the populations in the life history were from going up to balance;3. The major controlling factors to the population were the death of 1st generation by rain and wind, of the 4th-5th instar larvae and pupae of 2nd generation parasitized by insects and of 3rd generation by picking fruit,natural enemies and dying out of winter;4. The key factors were the predation of natural enemies to the 4th-5th instar larvae 1st generation,the pupae of 2nd generation parasitized by insects and the 4th-5th instar larvae of 3nd generation parasitized by funguses and the pupae of 3rd generation dying out in winter;5. A new method suggested by the authors was what the key factor analysed by using the grey sequence degree.