The K cycle of rubber tea chicken eco agricultural model, a typical tropical agro forestry system in Wenchang municipality of Hainan Province was studied with quantitative experiment and qualitative analysis, compared with rubber and rubber tea. The results showed that the K cycling rate, K output and K surplus in soil of rubber tea chicken agro forestry system were all the highest, being 59%, 134.5 kg/hm² and 168.2 kg/hm², respectively. The ratio of K output to K input of chicken sub system was 91% and the ratio of K output to K input in chicken products was only 23%. Amount of cycling K inside chicken garden is the highest, being 414.9 kg/hm², the K cycling structure of rubber tea chicken agro forestry system is more reasonable structure, and its K cycling was the most active.