The paper takes embedded devices which consist of ARM Cortex M3/M4 core as the foundation, studies on solution of realizing DHCP client based on none operating system. Checking schemes of transport layer UDP are optimized. Static memory allocation is used for optimizing the running efficiency of DHCP and stability of the system. The optimization algorithm of resisting ARP spoofing in the process of DHCP is proposed. In order to improve the DHCP client network security and service performance, a method of updating the whole LAN's ARP caches according to DHCP ACK is provided.