Abstract: Change of the environment by natural barriers (e.g. lakes, mountain ranges) and/ or human activities (e.g. major roads, agriculture, dam) can lead to the difference on diversity and change of seasonal dynamics of parasite communities by affecting population size and dispersal pattern of species in nature. In order to study the influence of characteristics on parasite communities in the Danjiangkou Reservoir Area, we investigated the infra- and component communities of intestinal helminths in the common carp Cyprinus carpio before the Middle Route of the South to North water Transfer Project was constructed in the Hanjiang River from February 2004 to November 2005. In investigation, a total of 11 species of intestinal helminths were recorded from 206 fish, including 3 digeneans, 5 nematodes, 2 acanthocephalans and 1 cestode and the statistical analysis of infective status of helminth population and community were performed at the same time. The total prevalence was 45.63%, and the mean abundance of helminthes and the intensity of infection being 4.23?2.65 and 9.29?7.48 respectively. Among the 11 species sampled, Aspidogaster ijimai had the highest total prevalence (25.24%) and mean abundance (1.76?.46), while Carassatrema lamellorchi had the highest mean intensity (25.00?6.68). The frequency distribution of helminths was over-dispersed in most of species as measured by the variance to mean ratio except that in low infective abundance, i.e. Cucullanus cyprini. The species diversity index of helminths communities was 4.63 as measured by Shanon-Wiener Index, and the species equitability index was 0.60. The analysis of seasonal dynamics of helminth community diversity showed that it possessed a fluctuant and irregular seasonal changes about helminth species composition and number. In common, each fish was infected with 1 to 4 species of helminths. In the helminth component communities, Aspidogaster ijimai was the dominant species, and the subdominant species were Asymphylodora japonica, Khawia sinensis, Carassatrema lamellorchis and Rhadinarhynchus cyprini, which were measured by important value index. Interspecific association analysis measured by coordinate coefficient indicated that there were significant positive associations between Rhabdochona cyprini and Carassatrema lamellorchi, Rhadinarhynchus cyprini and Aspidogaster ijimai, Contracaecum sp. and Micracanthorhynchina motomurai, Rhadinarhynchus cyprinid and Micracanthorhynchina motomurai respectively. The seasonal dynamics of prevalence and mean abundance of the dominant and subdominant species were measured by G-test of heterogeneity and Kruskal-Wallis H Test respectively. The result showed that most helminth species exhibited a very similar and significantly seasonal change pattern which had higher infection levels in autumn and winter and lower in spring and summer except Khawia sinensis which had no seasonal changes being found. The result of the present data showed that helminth infra-communities in common carp of the Dangjiangkou Reservoir Area would be relatively abundant, which reflected a relatively satisfactory survival environment including copious food and favorable water quality for fish hosts. While most of these infections focused on a few of the dominant and subdominant species and presented a distinguished seasonal dynamics, which revealed a nice subsistence strategy.