The characteristics of gas-centered swirl coaxial (GCSC) injectors used in a staged-combustion cycle of Russian liquidrocket engines were investigated. This study determined how the spray characteristics of GCSC injectors are influenced by the momentum flux ratio, gap thickness, and recess length used as important coaxial injector parameters. The film thickness and spray angle were measured by the electrical conductance and backlight image methods, respectively. The liquid film thickness and spray angle were changed according to the spray condition. The spray characteristics at low liquid pressure drop were sensitive to gas but not at high liquid pressure drop. The momentum flux ratio showed a better relationship with spray characteristics than the spray condition of liquid and gas, respectively. As the momentum flux ratio increased, the spray characteristics tended to decrease overall and this tendency occurred at a lower momentum flux ratio as the recess ratio increased. Also, the spray characteristics varied with the gap thickness. The liquid film thickness and spray angle were relatively low in small gaps, and were similar as the gap thickness increased.