Global species diversity is a historical result of speciation minus extinction and can be exhibited by phylogenetic patterns, whereas speciation is a process that may concern reproductive isolation and relating, at least in most sexual reproductive insects or other similar animals, to genital morphological evolution. The aedeagus is male genital organ that determines valid mating and reproductive isolation. However, definite correlation between aedeagus variation and species richness has not yet been clearly demonstrated. Here the phylogenetic tree of the rove beetle subfamily Staphylininae is built up based on 3085 bp DNA sequences of cytochrome oxidase subunit I (COI), nuclear 28S rDNA, nuclear genes wingless (Wg) and topoisomerase I (TP). Branching times and confidence intervals are calculated with molecular clock calibrations based on rove beetle fossil records. Different types of aedeagus, namely, median lobe plus a single paramere (Asp), a pair of parameres (App), or a single but bifurcated paramere (Abp), are marked on the phylogenetic tree and the genital morphological variations are compared in different genus-level taxa. The result shows that active cladogeneses occurred during late Cretaceous to late Paleogene, with those clades of Staphylininae evolved to be a more species-rich ones accompanied by larger aedeagus modifications. This implies that male genital morphological evolution might promote rove beetle speciation.