A dynamic time delay model for load balancing was proposed in distributed heterogeneous system by Hayat. But how to compute the load-transfer delay and the gain coefficient were not gived, so it is imposible to quantitatively analyse the performance of a distributed system. In this paper, an improved dynamic load balancing model with load-transfer delay is designed for LAN, and the gain coefficient is defined by a number of simulation test, so to meet requirements of LAN. At last, the simulation test is presented. The conclusion is that the improved algorithm not only saves the resources, but also realizes a reliable and efficient operation of the system. So the improved algorithm can be used to the distributed system in LAN.