In view of the contradiction between the high filling cost of the mine goaf and the difficulty in the treatment of large quantities of coal based solid waste mainly composed of gasification slag generated by the coal electricity chemical industry, the strength performance of paste filling materials with high content of gasification slag is explored by taking the gasification slag produced by Ningxia Yuanyanghu Power Plant as the research object. In this study, gasification slag is used as aggregate and cement is used as gelling agent. In the early stage, the reasonable range of three factors, namely, the amount of gasification slag in the dry material (X1), the bone glue ratio (X2), and the slurry concentration (X3), has been determined through single factor tests. Using response surface method, 17 groups of central combination tests have been designed to explore the influence of the three factors and the interaction between the three factors on the strength of paste filling materials. The three factors and 7d The functional relationship between the strength of filling materials at the curing age of 14 days optimizes the proportion scheme of paste filling materials. The results show that the bone glue ratio is the primary factor affecting the 7d and 14d strength. The interaction of bone glue ratio and slurry concentration has the largest impact on the 7d strength, and the interaction of the amount of gasification slag in the dry material and bone glue ratio has the largest impact on the 14d strength. The optimum ratio parameters were obtained as follows: the content of gasified slag in dry material was 49.282 %, the bone glue ratio was 4.554 : 1, and the slurry concentration was 81.056 %.