The optimum measurement for sea cucumber Apostichopus japonicus body weight and coelomic fluid is an essential experiment for the related research. The results show that the body weight is suitable to weigh in 20～30 min after being taken away from culture water (below 20 ℃). The proportion of coelomic fluid to the total body weight was also examined for small, medium and large sized sea cucumbers, at 26.88±1.39%, 25.24±2.91% and 30.98±1.86%, respectively. The safe dose of coelomic fluid extraction was less 1.5% to the total body weight of sea cucumber for ensuring physiological stability and survival of the tested animals. The results illustrated that the total cells of sea cucumber experienced a process of significantly reducing to slowly recovering. The resume process was asynchronous for different kinds of coelomocyte. The results show that the resume period for total cells, granule cells, transparent lymphoid cells and the absorbency of coelomic fluid are 4 d, 6 d, 6 d and 5 d, respectively. The measurement of body weight, the proportion of coelomic fluid to the total body weight, the safe dose and the resume process of coelomic fluid is firstly reported in sea cucumber Apostichopus japonicus. This research could be helpful for further study on physiological, immunological and zoological research in sea cucumber..