The researches of the structural and electronic properties of silicon and germanium clusters are of great significance for developing novel microelectronic materials. This paper aims to study the geometric structures and electronic properties of SimGen (m+n=9) clusters by combining genetic algorithm and density functional tight binding method. The study shows that there are two low energy stable atomic stacking configurations for SimGen(m+n = 9) clusters: one is a pentagon double cone stacking two small adjacent pyramids, the other is a tetrahedron close packing with a Ge atom on a bridge. Both stacking configurations are changed greatly with gradually increasing the Ge atom number in the cluster. The shape of the lowest-energy configuration changes from the pentagon double cone stacking two adjacent pyramids on the same side into the pentagon double cone stacking two adjacent pyramids on both sides of the up and down. With this change, the electron distribution and the gap of the highest occupied molecular orbital and the lowest unoccupied molecular orbital gap are obviously dependent on the difference in components of Ge and Si elements contained.