The spray characteristics of the oxidizer-rich preburner are investigated. This system is generally operated at an oxidizerfuel mixture ratio of 50. The spray quality and mixing performance are very important for safe combustion. To know the spray characteristics of the oxidizer-rich preburner, we have designed various swirl injectors and measured droplet velocity and size by the PDPA system. The flow discharge coefficient of the fuel orifice is $0.12{sim}0.21$, oxidizer orifice discharge coefficient is $0.16{sim}0.28$. From the spray visualization, fuel nozzle spray angle is $15^{circ}{sim}25^{circ}$, oxidizer nozzle spray angle is $65^{circ}{sim}85^{circ}$ and combined spray angle is reduced $2^{circ}{sim}5^{circ}$ compared to the oxidizer nozzle only case. From the PDPA measurement, droplet SMD is $175;{mu}m$ at 50 mm and $190;{mu}m$ at 100 mm of variant 1 combined case. The number concentration measurement revealed the reason of the droplet diameter increasement with distance. That is due to drop coalescence results from collision of drops which is occurred in dense sprays at a long distance from nozzle orifice exit.