The two-phase mosaics of vegetation alternating with bare ground,was frequently observed in arid ecosystem. Theoretical studies suggest that this range of spatial patterns is the result of self-organization as a consequence of resource redistribution.On the basis of the review of self-organized process of vegetation,the spatial patterns and self-thinning process of Haloxylon ammodendron plantation for more than 40 years were analyzed in an oasis-desert ecotone in the Hexi Corridor.Results showed that a self-organized process of sand-fixing plantation would also take place in arid areas especially where precipitation is less than 200 mm.The overall spatial pattern of H.ammodendronshifted from initially uniform distribution to clustered,the landscape patches are becoming fragmented.But the self-thinning process of H.ammodendron plantation don't follow the natural order of the developmental stages,it is most relevant to the distance between the habitats of H.ammodendronand oasis marginal,and the groundwater depth in the habitats of H.ammodendron plantation.Ecosystem may abruptly shifted from one alternative stable state to another one,accompanied with great changes,under climate change and exacerbated human disturbance,the research of threshold range of vegetation pattern regime shift should be strengthened in the future,and the research of self-organized process of the sand-fixing plantation in the arid areas should also be strengthened.