With the purpose of improving the assembly performance of an Optical Burst Switching (OBS) network,the assembly modular for the edge node of the OBS is studied in this paper and a novel design scheme for Assembly Controllers (AC) is proposed. By introducing the feedback of BDP sizes,a time-threshold based modular is changed into a closed-loop system different from former assembly modules using an open-loop system. By measuring the network traffic flow,a suitable time-threshold for a timer is chosen according to the control curve of the novel modular,meanwhile,the control curve is modified according to the BDP size feedback. Simulation results show that the novel modular can improve the distribution of BDP size by 4.95%,and decrease the assembly delay by 15％ as compared with that of the time-threshold based modular. Therefore,the novel modular can not only adjust the time threshold according to the traffic flow,but also can control the distribution of BDP sizes.