This paper introduces the basic concept and principle of data fusion technology,and takes the data of two inertial measurement units in a high-speed ballistic testing system of a mine as an example. The application of weighted average data fusion method in underwater ballistic testing is described. Multi-source data from the high-speed ballistic testing system is fused and analyzed,and the results show that this data fusion method can smooth the data effectively,reduce data discontinuity or jump and other adverse effects,and improve the confidence level of ballistic measurements with multi-source,large spatial and temporal coverage.