Abstract: In order to study the height development of water conducted zone in coal seam overburden under the condition of thin bedrock and thick loose layer, engineering test was carried out in 3301 working face of Sanyuan Coal Mine, Shanxi Province. Based on the empirical formula method, the height of water conducted zone under overburden condition of No.3 coal seam in 3301 working face of Sanyuan Coal Mine was theoretically predicted. The method of numerical simulation was used to analyze the dynamic change process of the height of the subsidence water conducted zone under the distribution condition of No.3 coal seam overburden. The height of water conducted zone in 3301 working face was observed by field test using the method of staged water injection observation in underground coal mine. The results show that the height of water conducted zone in 3301 working face of Sanyuan Coal Mine obtained by the above three methods is 62.9 m, 64.0 m and 61.1 m respectively, and the obtained results are very similar. In order to ensure safety, the height of the water conducted zone should be 64.4 m, which is the maximum value observed in site.