Abstract: In this paper, it is reported that the activities of Hill reaction in the chloroplastic fragmental suspension (CS) and the cell homogenate (CH) of hybride and their parents and the complementation of parents have been measured with Clark electrode among five hybrid rice combinations at seedling stage. Activities of Hill reaction not only in CS aud CH from hybrids but also in the mixture in vitro of CS from biparents or of CH of biparents are higher than the means of activities between biparents, those are heterosis and complementation And the complementary effect of CH is higher than that of CS, It is obviously shown that the heterosis and the complementation of activities of Hill reaction, no matter what is in CS or in CH may be a physiologic and biochemical index of hybrid vigor prediction and that these results are of important significance in study on the mechanism of heterosis. In addition, the method of the cell homogenatc complementation is more convenient, stable, reliable than of the organelle complementation in hybrid vigor prediction.