In the literature on solar cells , the relationship curve of output current versus output voltage and therelationship curve of output power versus output voltage are generally given. However, it is rare to see therelationship curve of output voltage versus load resistance ,the relationship curve of output current versus loadresistance , and the relationship curve of output power versus load resistanee. These curves are studiedexperimentally and theoretically here.The results of experimental tests and theoretical calculations are quiteeonsistent.Both of them show that , for a determined solar cell circuit, with the increase of load resistanee , theoutput voltage monotonically inereases and the output current monotonically decreases. However, the outputpower does not change monotonically ,there is an optimal power value.'This optimal power value corresponds toan optimal load resistanee value.In addition , we have also studied the impact of incident light intensity on theoutput voltage ,output current and output power of solar cells, and found that all these outputs increase with theinerease of light intensity.The results of this work are of great significance in the design and application of solarcell circuits.