Program dependency graph usually judges the data dependency according to definition-use relationships of variables in statements, and it cannot make an accurate judgment according to the semantics, which leads to the introduction of false dependency relationships and the repair failure caused by the use of error information in repairing defects. Therefore, this study will prune false dependencies related to null objects or null pointers by using abstract attributes and propose an abstract semantic-based program dependency graph to reduce the analysis of dependency relationships unrelated to the semantics of program defects and repair null pointer references. Based on the dependency relationships obtained from the analysis, a multi-strategies repair scheme is implemented under the guidance of different repair strategies for null pointer references, and the null pointer references are repaired with side effects minimized as much as possible. In addition, in this study, the null pointer references in Defects4J are adopted to evaluate the repair tool DTSFix through experiments. The results show that the repair effect of DTSFix is much better than that of other tools, which proves the effectiveness of the method.