A hierarchical diversity index--taxonomic distinctness index delta+, which was first defined by Warwick and Clark in 1998, was employed to evaluate the pollution status of the Bohai Sea with freeliving marine nematodes. The result showed that the Bohai Bay and other coastal sampling sites might be affected by oil and gas production and other anthropogenic influences. In other words, anthropogenic disturbance was affecting this component of the benthos in these locations. And most offshore sampling sites in the middle of the Bohai Sea were clear and unpolluted.