The geometric effects of turbulent jets with or without axis-switching are numerically investigated. The fluid combination is selected by varying density ratio for 0.067 [Hydrogen/air], 0.55 [Methane/air], 1.0 [air/air] and 1.6 [propane/air]. In order to analyze the effect, various jet behaviors of non-circular jets, including velocity decay rate, potential core length, secondary flow structure, jet spreading, and mixing efficiency are compared to its counterpart circular jet in each four cases of variable-density. It is interesting that the geometric effect is more clear in the jet which has high density difference. This trend is further pronounced by the axis-switching phenomenon.