Abstract: The estimation condition of quiescent operating point and the estimation method of coupling capacitor at the load side in the votage-divided bias common emitter amplifier circuit are researched in this paper. The circuit parameters constraint relation required to estimate the quiescent operating point is proposed by analyzing the relative error between the calculation formula and the estimation formula of the quiescent base potential in direct current path. After the low frequency small-signal equivalent circuit is obtained by the supply fluctuation signal, the method for reducing amplitude distortion of output signal is proposed by estimating the value of coupling capacitor at the load side in the capacitive impedance range. The correctness of the approximate calculation which is verified by the software simulating provides convenience and theoretical basis for circuit design, estimation, and experimental debugging.