Abstract: Testing coverage is one of the most important metrics in evaluating how much of a program is tested. Unfortunately, in the field of timing sequence test for parallel programs, there is very little work about the quantitative analysis of coverage. Here proposed is a numerical calculation scheme to measure the coverage for the timing sequence test of distributed programs. It is based on a SYN sequence model and atomic event testing strategy. With the distributed implementation of tree topology broadcast and combine as instances,the process of analysis and calculation of the testing coverage is further clarified. Because distributed broadcast and combine are two typical operations,the numerical method for the coverage of timing sequence presented here can also be applied to other practical distributed programs.