A combined computational and experimental investigation to examine temperature and soot volume fraction in coflow ethylene-air diffusion flames was presented.A numerical simulation was conducted by using a relatively detailed gas-phase chemistry and complex thermal end transport properties coupled with a semi-empirical two-equation soot model.Thermal radiation was calculated using the discrete ordinates method.An image processing technique and a decoupled reconstruction method were used to simultaneously measure the distributions of temperature and soot volume fraction.The results show that the maximum error for temperature does not exceed 10％ between the prediction and the measurement.And the maximum error is 6.9％ for soot volume fraction between prediction and measurement.Additional simulations were performed to explore the effects of global equivalence ratio on diffusion flames end the soot formation.The results display that the soot formation increases with decreasing the coflow air velocity.And the soot formation in each ease appears in the annular region,where the temperature ranges from about 1000 K to 2000 K and the profile becomes taller and wider when the coflow air is decreased.