Abstract: Five morphologic indexes of Cyclocarya paliurus seeds from 15 provenances were measured and the trend surface analysis method was aclopted in this paper. The results showed that there were extremely significant differences in 1000-grain weight, seed size, seed diameter and seed thickness among 15 provenances but no significant difference in diameter to thickness ratio of seed was observed among the provenances. The 1 000-grain weight presented a southwestnortheast variation. The thermal energy and water had an interactive effect. A center-round variation existed at the seed size, and it was rarely affected by climatic factors. The seed thickness, which was mainly related to mean annual temperature and frost-free period, was proved to have south-north variation at same longitude. However, there was no significant trend of geographical variation in seed diameter.