Abstract: Based on the theoretical model of photocarrier radiometry (PCR) testing solar cells, numerical simulation analysis was proceeded to study the influence of different circuit states in frequency domain response signal, and amplitude response curves were achieved with different external load resistors. Experiments were carried out with built set-up for photocarrier radiometry diagnostic approach for Si solar cells. The feature of amplitude diagram and phase diagram were stated. The effect of different circuit states on test results was discussed. At last the fitting life time was compared in different circuit states to study whether circuit states affect the carrier parameter measurement. The results shows that open circuit state gives the highest amplitude in amplitude diagram, and the smaller the load resistance is, the lower amplitude becomes. However, phase didn't change clearly. The fitting life time is nearly consistent, not changed with circuit states, which shows the results of PCR testing solar cells in open circuit states can forecast frequency domain response results and carrier parameters fitting calculation in other circuit states.