Tobacco caterpillar, Spodoptera litura (Fabricius) is an important insect pest on tobacco and taro causing serious damage by defoliation. In order to master the control effect of different factors on S. litura, the life table of natural population of S. litura on tobacco and taro were studied. The results ndicated that the increasing populations of S. litura of 2^nd and 3^rd generations on taro were all higher than that of S. litura of 2^nd and 3^rd generations on tobacco in 2005 and 2006, respectively. Among different factors of S. litura on tobacco and taro, “predators and others” was the most effective factor. If all natural factors were excluded, the indices of population trend (I) of S. litura of 2^nd and 3^rd generations would increase 31.2029 and 50.0371 times on tobacco, respectively and increase 29.3492 and 41.2873 times on taro, respectively in 2005, while the indices of population trend (I) of S. litura of 2^nd and 3^rd generations would increase 33.1421 and 75.4167 times on tobacco, respectively and increase 31.5357 and 70.5355 times on taro, respectively in 2006. From the results, we may suggest that these natural factors, a certain extent, have a good control effect on the population of S. litura, and the control effect of these factors on tobacco was better than that on taro.Key Words: Spodoptera litura; tobacco; taro; functional factor; life table