Alloptical buffer can store the packet in optical domain without the opticalelectronicoptical conversion and becomes the important element in alloptical network. Its performance greatly influences the loss packet probability of network. But in semiconductor optical amplifier (SOA) cross phase modulation and cross gain modulation are coexisting. So in recircular alloptical buffer based on SOA, the output power between stored packet and packet without being stored is unbalanced and bit-error ratio of network increases. After analyzing the working principle of alloptical buffer, a new method for power equilibrium in recircular alloptical buffer based on SOA is presented. By changing the usual positive control pulse to negative and using an electronic variable optical attenuator, the buffer gets an uniform output power and its performance is improved markedly. This method can be applied in all recircular alloptical buffer based on SOA.