The work aims to solve the high temperature corrosion and erosion caused by the coal ash/flue gas of boiler flue gas side and prepare excellent coating structure to prolong its service life. Ni-Cr coating was successfully prepared on the surface of TP304H austenitic stainless steel through the plasma powder cladding technology. The influence of cladding parameters on coating microstructures were studied and the corrosion behaviors of Ni-Cr coating were investigated respectively in simulated coal ash/flue gas environment for 650 ℃ and 750 ℃. The microstructures of the cladding coating, and morphologies, compositions and phases of the corrosion products were analyzed using SEM, EDS and XRD. The Ni-Cr coating thickness increased obviously with the increase of cladding current which the maximum thickness is about 1.3 mm and the maximum thickness appeared with the increase of powder feeding rate which is about 0.93 mm. The composition of coating is mainly consisted of (Ni) and Cr2Ni3. The corrosion resistance of Ni-Cr coating are obviously different in the coal ash/flue gas environment for 650 ℃ and 750 ℃. The good corrosion resistance of coating and corrosion products of continuity and integrity are observed at 650 ℃. The oxide of Fe and Cr is the main corrosion products for all of samples, while a small amount of sulfide is discovered. After 750 ℃, the maximum corrosion depth is more than 4 times as long as 650 ℃ for 500 h. The intercrystalline corrosion is primarily resulted due to the collapse of corrosion products. The perfect combinated structure of Ni-Cr coating and matrix, uniform tissue and dendrite growth state, are obtained by controlling the cladding current and powder feeding rate. The high Cr content coating can well protect matrix alloy in the environment of high temperature coal ash/flue gas corrosion.