Prestalk and prespore cells of Dictyostelium discoideum were separated and obtained by centrifugation of Percoll density gradients, and the expressions of gp150 and Caspase-3 in these two types of cells were analyzed by western blot. The results showed that gp150 could only be detected in prestalk cells, and the quantity of this protein increased with the development of cells. This suggested the quantity of gp150 expression had a close relationship with both of developing time and the differentiation of prestalk cells. It also showed that apoptosis proteins with the molecule weight of 31.5 kD and 37.5 kD were detected in prestalk cells and their quantities also increased with developing time. Besides, proteins of 38.2 kD could be detected in both of two types of cells. These results indicate that proteins like Caspase-3 are expressed in the progress of prestalk cell differentiation, and they are deeply correlative to the progress of apoptosis There could be a relationship between the expression of gp150 and Caspase activation.