Modularity equation plays an important role in the eld of information fusion, which helps to select aggregation functions and reduce the failure rate in the process of aggregation. Based on this, we focus on the study of modularity equation between overlap (grouping) functions and semi-t-operators. We give the solutions of this equation between overlap (grouping) functions and semi-t-operators with continuous pseudo-t-norm or continuous pseudo-t-conorm in the corresponding cases.