The results of ecological experiments on adult Sipunculus nudus reveal that within 48hours,its tolerances of both temperature and salinity vary from 0～40℃,6～57 respectively.Its optimal tolerance ranges are 16～34℃,21～42 respectively.Fluctuations in both temperatures and salinities have no direct impact on the worm when two of them are in optimal threshold.Two ranges,high and low,for temperature and salinity tolerances are given,in which the changes in low ones with t=0～16℃,S=6～21 have positive relationship with the tolerances of this sipunculid worm,and variations of high ones with t=36～40℃,S=45～60 showing reverse relationship.In these two ranges,the worm is subject to variations in these two ranges,high or low,displaying abnormal physiological responses.High thermal threshold is 42℃ for the worm's mortality at a salinity of 32,and the high and low salinity thresholds are 60 and 3 respectively at a temperature of 26℃.Qualitative description and quantitative definition of relationships between the changes in both temperature and salinity and physiological responses and survival rates of the worm have profound implications in terms of its ecological theory and production practice.