Oxy-fuel combustion of heavy oil can be applied to oil field steam injection boilers, allowing the utilization of both heavy oil and CO2 resources. The present study investigated the oxy-fuel combustion characteristics of heavy oil under different conditions, including the flame, temperature, and pollutant emission characteristics. The results showed that heavy oil combustion was stable at O-2 concentrations of 29%, as the O-2 concentration was increased, the flame began to brighten gradually, becoming shorter and thicker, while the temperature gradient became higher and the high temperature zone moved closer to the burner exit. The overall temperature and the combustion rates in O-2/CO2 atmospheres were below those seen in O-2/N-2 atmospheres. The volume of NO emitted in the flue gas was almost unaffected by the change in O-2 concentrations in atmospheres containing high concentrations of CO2, but it increased rapidly with increasing O-2 concentration in O-2/N-2 atmospheres. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.