Based on the land use data of the Lancang River watershed(LRW), the center of longitudinal range gorge region(LRGR) in 1985, 1995 and 2000, supported by GIS, and with the indexes of fragmentation, isolation and dominance，and of vulnerability of landscape types, it was analyzed that the temporal and spatial characteristic of landscape ecological security(LES) in LRW. The results showed that there were difference change trends for different landscape types in this region, the transformation from one landscape type to anther was very complex and that was mainly happened among farmland, woodland and grassland. It was found that the change of landscape structure can strongly influence the temporal and spatial distribution of ecological security index (ESI) under natural and human factors, which might result in the decreasing of the degree of ecological security (ES) during 16 years. The large difference on the distribution shapes of ESI and its annual decreasing rate were found among the upper, middle and down stream due to the especial terrain and physiognomy in LRW, i.e, the rate of ESI in down stream descend the fastest, then the middle stream, and its of upper stream changes slowly because of locating high altitude and disturbing weekly by human activities. The lower ESI(ES ≤ 05 ) were mainly distributed in down stream with shape of “Y” in NE-SW and spread along the river. And the higher ESI (ES≥0.6) were mainly distributed in the middle stream with SE-NW direction and shrunk along the river. Human activities were mainly carried out on landscape level and landscape was also one of the basic units of the regional ecological environment management. Therefore by using the method of landscape to study on the ES, to discover the alteration character among different landscape types and then identify the change tendency and its inner factors of the regional eco-environment might be important for regional eco-construction and natural resource exploitation.