Abstract: The survey of forest gap character of degradation mangrove has important ecological significance, which could provide reference for the development and protection of Techeng Island mangrove. This paper investigated the whole piece of degraded mangrove forest of gap size structure, mode formation, character of forest gap maker and gap border trees in Techeng Island, Guangdong province.The results showed that: mangrove forest gap was main of small area of forest gaps, shapes was most similar to ellipse,the average height of forest gap was low. Most gaps were created by a combination of natural death, breakage on branch,stem breakage+natural death,which first reported forest gap forming new way of hydrological effect of seawater unique belong to degraded mangrove forest and after the formation of gaps, Sporobolus virginicus invade. The numbers of gap maker were more significant than health mangrove forest gap, diameter incline to small, with mian for Avicennia marina and Rhizophora stylosa.Gap border trees were mainly small and medium diameter, with poor health mostly distributed in low tide and middle tide, had the trend of deterioration. We concluded that degraded mangrove forest gap presented the different character of the healthy forest gap, the excessive erosion of sea wind, and wave was the main inducement.