The community structures of macrozoobenthos and bioassessment of water quality in a second order river—Tanqigou stream of Qingjiang River Basin were investigated from April 2006 to March 2007. Altogether 82 species of macroinvertebrates were collected, among which aquatic insects were 70 species, belonging to 45 genera in 27 families under 7 orders. The community structure exhibited an obvious spatial and temporal variations. Site S2 with fringe effect possessed the largest number of species, and most of the macroinvertebrates presented in April with 61 species sampled, more than those in other months. Over 60% of the collected species could inhabit in the six types of microhabitats. Biodiversity in spring was the largest, and followed summer, winter and fall in rank. The density of the community reached its peak in April at 3293ind./m², while biomass attained its peak in December at 163g/m². The water quality was bioassessed with Shannon-Weaner diversity, Biotic Index and Family Biotic Index, and totally it was fairly clean during the sampling period. Considering the coincidence with physical-chemical parameters, BI and FBI bioassessment methods were fitter to apply in this region .