The relationship of the oxygen consumption rate (OCR) of Hyriopsis cummingii with body size and temperature in standard metabolism was studied under controlled laboratory condition in this paper. The results indicate that size of individual, water temperature and both together have significant effects on OCR (P<0.01). Among these effects, effect of body size>that of temperature>the mixed effect. OCR decreases as the increase of body size and there is a negative exponential regressive function OR=aW~(-b),b value of 0.7715-0.9709, With a mean value of (0.875). The experiment indicates OCR rises with the rise of temperature in a temperature range; nevertheless, OCR decreases and even the respiration of Hyriopsis cummingii ceases when exceeding the upper critical point.