Three polypropylene (PP) and one polyethylene (PE) microporous hollow-fiber membranes were used in direct contact membrane distillation (DCMD) and vacuum membrane distillation (VMD) for the desalination of simulated seawater. The influence of feed temperature and feed flow on distillate pure water flux was investigated. The comparison of the PP and PE membranes in DCMD and VMD was carried out. It was found that the water flux increased with the feed temperature and feed flow in both DCMD and VMD. The data also showed that, compared with the PP membranes, higher water flux could be obtained by using PE membranes in both the DCMD and VMD processes.