In this paper, a pilot vacuum membrane distillation device, using polypropylene hollow fiber, was designed and installed on a seagoing vessel to investigate the operating conditions. During operation, the incoming seawater was heated by the waste-heat generated from the vessel engine. It was found that this device could reach a desalting degree of 99.99% and a membrane flux of 5.4 kg/m(2)h at 55 degrees C and -0.093 Mpa. The results obtained from this pilot test are in accord with the previous lab experiment results.