Abstract: Cyclocarya paliurus is a typical heterodichogamous species which contains two mating types in populations: protogyny(PG)and protandry(PA). Flowering phenology of female and male functions segregation within PA or PG, and synchronization between PA and PG may greatly affect seed quantity and quality for C. paliurus population. To determine the sex-expression of C. paliurus, we monitored flowering phenology for 2 years(2014 and 2015), including the ratio of flowering phenotypes, the flowering order of male and female inter and intra two mating types, flowering duration and flowering overlapping characteristics based on 7-year plantations growing in Taofeng in Liyang city of Jiangsu Province and Hongyashan Forest Farm Anhui Province. The results showed that flowering period of C. paliurus was from late April to late May, with fluctuation by changing of environmental factors. Duration of stigma receptiveness and pollen shedding lasted 9-19 days(with the longest period of 21 days)and 2-9 days, respectively. There were two categories, five flowering phenotypes in immature plantation: monoecious types containing protogyny(PG), protandry(PA)and synchrony(SC); unisexual type including female(F)and male(M). The phenomenon that the majority was female individuals and less was monoecious plants were found through observations of two plantations. In 2015, flowering rate in Taofeng of Liyang city was up to 73.2%, of which 28.8% individuals were monoecious plants, with the ratio of 1:1.2 for PA and PG. However, flowering rate in Hongyashan Farm was only 38.6%, of which 16.7% individuals were monoecious flowering phenotype, bias to PG. It was found by two consecutive years' observations that the changes in mating category occurred mainly from unisexual to monoecious types; the expressions of PA and PG individuals were stable, and inverse changes were very few. Within monoecious type, 52.2% individuals whose female and male flowering time were completely separated, and 47.8% individuals were partly(rarely completely)overlapping. The results of correlation analysis showed the expression of flowering was significantly influenced by growth condition of plants. The rank of flowering phenotypes based on average basal area is PG＞PA ＞M ＞F ＞non-flowering. The results of Duncan's multiple comparisons showed the average basal area of monoecious types were significantly different from unisexual ones. Among flowering category, no significant difference for average basal area was found among PG, PA and M types. However, significant difference occurred between F type and three types(PG, PA and M types). It seemed that flowering or not, and flowering phenotype obviously affected by nutrient accumulation of plants.