The influences of doping whit congeners on the band topology in half Heusler-type of NaAlGe alloys are investigated using the first-principles calculations. It is found that the Na1-xCsxAlGe alloys with a normal band order are converted into topological nontrivial phases when x is up to 0.125. We argue that it is the degree of hybridization between Al and Ge determine the band order at the Fermi level. The Na or Cs only plays a role of the valence electron contributor and influences the lattice parameter.