Sampling from sediment and environmental factors for investigating the structure and population dynamic of macrobenthos community in 5 stations in lagoon Lipar located 19 k.m. east of chabahar in sistan and balouchestan province from NOV in 2013 to APR in 2014. Mean density of macrobenthos in station 3 with 1441 ind/m2 was maximum during 6 month sampling period and density for stations 5, 4, 2, 1, was 1043, 580, 141 and 108 ind/m2 respectively. Macrobenthos density was also maximum in May with 1078 ind/m2 and 717, 675, 541, 523, 441 ind/m2 was for Feb, Mar, Des, Jan and Apr respectively. Among macrobenthos community only 3 groups, including chironomids with 8873, Foraminifrans and gastropods with 2162 and 10 ind/m2 were abundance respectively. Among environmental factors, salinity (mean: 137±90 ppt) and temperature (mean: 25±5O °C) poss the highest variation. Results show that between macrobenthose and sand grain was a significant correlation (P<0.05). According to results it seems that the lipaar ecosystem is in stress condition because of high temperature, low rainfall, high evaporation, high content of organic matter and fine grain structures in most stations and sensitive groups under stress condition omitted from the environment and tolerant groups to bad condition exist in ecosystem.