Abstract:Through the experiment by split block design，and variance analysis as well as offsetting analysis from the normal distribution，the paper enclosed the systematical studies on the status of settlement and competition of three arbor mangrove species-Bruguiera sexangula (Lour) poir，B．gymnorrhiza (L) Lamk and Rhizophora stytosa Griff after they were introduced artificially into a degraded dense Aegiceras corniculatum+Ceriops tagal Community，and revealed the influences of the serial of thinning bush measures before introducing upon their settlement．Variance analysis shows that thinning the bush in plot way is obviously good for increasing the survival rate of R．stylosa and for promoting the growth of B．sexangula．Offsetting analysis from normal distribution shows as follows：B．sexangula in competition with the bush results in left offsetting seriously (off-setting ratio equaling 5.69)after two years and seven months，which means that the bush has a great unfavorable influence upon its growth，it is necessary to adopt the measures again for controlling the recovery of the bush．B．gymnorrhiza and R．stylosa develop into left offset slightly(offsetting ratio equaling 2.54 and 1.85 respectively which basically belong to normal distribution，this means that the bush has a very small unfavorable influence upon their growth，so that the improvement of A． corniculatum+C．tagal community will have more certainty of success．Based on analysis of the morphology and development in combination with offsetting analysis from normal distribution，it is concluded that B．gymnorrhiza and R．stylosa are more shade-tolerant tree specties，B．sexangula is light-demanding tree speies．