An enrichment system for volatile organic compounds (VOCs) in ambient air based on adsorbent tube sampling/cold trap focusing method was developed. The VOCs in ambient air are sampled firstly by the adsorbent tube, and then focused on the cold trap. After the cold trap thermal analysis, the VOCs enter the GC-FID system with the high purity carrier gas. The performance of the system was measured by using standard gases(benzene, methylbenzene, ethylbenzene). The experimental results show that the cold trap designed by this system has a focusing efficiency of more than 90% for VOCs (benzene series), and relative standard deviation of standard samples is less than 3%, and the linear correlation coefficient is greater than 0.99. The system is stable in operation, and satisfies the demand for enrichment of VOCs in the ambient air.