In order to qualitative evaluation of the sediment samples, the samples were seasonally taken in the Tiab basin for one year from autumn 1994 to summer 1995. Four stations were considered to be sampled that the first was between the south and north Tibet, the second station is located to the south Tiab and the third station located at the subbranch of the canal and the station 4 at the branch of estuary. Two ecological indicators based on macrobenthos community were used to calculate ABC and w-statistic indices. Spatial distribution of macrobenthos density at four stations showed that station 4 with an average of 1467 individual per square meters had the highest density, followed by station 3, 1 and 2, respectively, with 652, 393 and 223 individual per square meters in ranking are next. Amount of weight-based indices showed that the frequency curve in the ABC index is located on the top of the weight curve at all four stations and the w-statistic index with the lowest value is -0.433 at station 2. The results of this study showed that, although at stations far from shrimp breeding grounds, the diversity is more than those are close to shrimp farms, but biodiversity figures indicate that all areas are affected by effluent from shrimp pools.