Based on the crystal silicon solar cells' power complete differential equation, and combined with the experimental facts that the open circuit voltage and power vary along with the cells'temperature and insolation, the independence of the parameters that determine solar cells' operating state is investigated. After a strict mathematic deducing process, it is concluded that the insolation, cells' temperature and load resistance are the independent parameters of crystal silicon solar cells, and that the series resistance is a function of cells' temperature. The series resistance's experimental results show the theoretical analysis's accuracy.