The crosstalk modeling of switching matrix based on the XGM in SOA for optical packetswitched networks is presented. Crosstalk-induced bit error rate (BER) and switch cascaded capability under unbalanced traffic are examined,which proves to be relevant to the SOA parameters,the traffic model unbalanced degree,the control pulse energy and so on. Several rules are drawn to facilitate the design of SOA-based switching matrix under unbalanced traffic.