Shock tube is used to study the ignition delay of RP-3 under ultra-low pressure (0.01-0.1 MPa). The ignition delay of RP-3/O-2/N-2 mixture is obtained with the characteristic emission signal of OH* radical at 306.5 nm and the pressure signal near the end of the driven section. The pressure range is from 0.01 MPa to 0.1 MPa, the temperature range is from 1113 K to 1600 K, and the equivalence ratio range is from 0.5 to 1.5. The influence of temperature, pressure, and equivalence ratio on the ignition delay characteristics of RP-3 is investigated. Results show that the increase in temperature and pressure and the decrease in equivalence ratio shorten the ignition delay time. The fitting formula of the relationship between the ignition delay time of RP-3 and temperature, pressure, and equivalence ratio under low pressure is obtained, and the results are verified by experimental data. (C) 2019 The Combustion Institute. Published by Elsevier Inc. All rights reserved.