Spray characteristics for APU gas turbine engine are investigated. In the test, four flight conditions such as sea level idle, sea level max power, 20,000 feet idle, 20,000 feet max power are used as spray experimental conditions. Spray visualization was performed by using ND-YAG laser bean PDPA(Phase Doppler Particle Analyzer) was used for measuring the particle diameter and velocity from 20 mm to 100 mm from discharge orifice. From the test result, SMD is $90{sim}95;{mu}m$ 맛 20,000 ft idle condition and SMD is $60{sim}75;{mu}m$ at sea level idle condition. Also SMD is $55{sim}65;{mu}m$ at 20,000 ft max power condition and SMD is $30{sim}70;{mu}m$ at sea level max power condition. In the case of 20,000 ft idle condition, combustion instability could be occurred due to the higher drop diameter. Therefore it is necessary to decrease the droplet diameter in the high altitude condition.