By the theory that change of interlaced zone can indicate change of its environment, the moving split-window technique was applied to the judgment of interlaced zone located in Siertan wetland, Yanchi County, Ningxia Hui Autonomous Region to confirm the causes of wetland changes. Besides, certain indexes like vegetation survey, biodiversity index and rainfall were also used for the analysis of changes of interlaced zone. The technique was suitable for judging the interlaced zone boundary of the Siertan wetland and the relative appropriate window width was found to be 8 quadrats. Meanwhile, the judgement results for the interlaced zone in the Siertan wetland showed that the wetland had the largest interlaced zone width, which was far away from the center of wetland under better conditions in 2007. However, all the indexes decreased with the increase of time from 2008 to 2013, and the conditions of wetland became worst gradually. It was the construction of railway in 2008 that truncated stream water supply, which led to the shrunk of the wetland. Therefore, it is beneficial to protect surface runoff system in developing economy so as to prompt the permanent development of wetland. It can also provide new solutions and ideas to find and solve protection and improvement problems of wetlands in semi-arid region.