Isopods of the genus Ligia are deemed as excellent pollution monitoring organisms for coastal zones. A species of Ligia cinerascens was chosen to be tested, which was collected from three coastal zones in Dalian, China. The concentrations of metals followed the order of Cu>As ≈ Cd>Pb. Ligia collected from a municipal sewage outlet in Heishijiao showed the highest level of metals. Ligia from a natural bathing beach in Changshan Island showed the lowest level of metals as expected. Ligia grown in the same site could accumulate different levels of metals due to their different body weight. Both males and females conformably accumulated heavy metals in bodies. Taken together, this work suggests that L. cinerascens can serve as a biomonitor species. Within the range of 0.3-0.9g body weights, body weight rather than gender should be taken into account as a factor in the process of environmental biomonitoring.