Abstract: In order to improve stability of environment monitoring system and save system's resource, the paper proposed a design scheme of environment monitoring system composed by lower computer, transmission network and upper computer. It introduced design of hardware and software of the lower computer in the system in details. The hardware of the lower computer takes ARM9 processor S3C2410 as core, its software uses multi-thread application program to process multi-task at the same time and uses semaphore and mutex to realize synchronization among threads. The actual application showed that the system runs stably and improves system efficiency.