1. The sexes of Limnoria are separate. The development of Limnoria tripunctata Menzies is direct, without any pelagic larval stage. The whole breeding process includes dispersal migration, copulation, development of embryo and larval hatching. 2. According to morphological changes, the life history of Limnoria tripunctata Menzies may be divided into following five stages: (1)embryonic development stage, (2)banana larva stage, (3)red-ege larva stage, (4)six-pair peraopod larva stage, (5)adult stage. The gribbles pass for the first three stages in brood pouch and live in burrows in the last two stages. 3. Although we may find the gravid female every month, but it does not mean reproduction all the year round. The newly hatching larvae were observed only in March under natural conditions. The breeding season of Limnoria tripunctata Menzies in the Qingdao harbor is from March to November, with a peak in April to July. 4. A total of 107 gravid females was examined. The number of eggs carried by a single gravid female vary from 3 (the least )to 21(the most). Most of the gravid female carried the eggs in number of 5-9 and 12-16 with the percentage of 44.8 and 32.7 respectively.