Abstract: Ignition delay characteristics of ethylene/O₂/Ar mixtures have been studied behind reflected shock waves in a shock tube by monitoring the steepest rise of the characteristic emission of OH radical at 306.5nm. Experiments were conducted with low argon dilution, covering a temperature range of 800～1650K, at pressures of 0.2, 0.7 and 1.2MPa, and with equivalence ratios of 0.5, 1 and 2. The oxygen content of the test mixtures was about 20%. The correlation formula of ignition delay dependence on temperature, pressure, equivalence ratios and fuel and oxygen mole fraction was obtained. The transition of ethylene ignition to detonation was observed with different initial temperatures, and the influence of initial temperature on ignition delay characteristics of ethylene was also discussed.