The hot tearing susceptibility of a Fe-20.96Cr-2.13Ni-0.15N-4.76Mn-0.01 Mo duplex stainless steel was investigated using method of constrained solidification shrinkage in one dimension.An apparatus for realtime measuring the contraction stress and temperature during solidification was developed,which can achieve the in-situ observation of melting and solidification and avoid the large temperature gradient of casting under the condition of pouring.The results show that the contraction stress increases significantly when the core temperature of casting reaches the liquidus temperature.The contraction stress is released when the core temperature of casting reaches 1456°C.At this temperature,the hot tearing susceptibility of duplex stainless steel is the largest.With decreasing the core temperature to 1363°C,the slope of contraction stress increases,which is related to the ferrite-to-austenite transformation. The hot tearing susceptibility of a Fe-20.96Cr-2.13Ni-0.15N-4.76Mn-0.01 Mo duplex stainless steel was investigated using method of constrained solidification shrinkage in one dimension. An apparatus for realtime measuring the contraction stress and temperature during solidification was developed, which can achieve the in-situ observation of melting and solidification and avoid the large temperature gradient of casting under the condition of pouring. the results show that the contraction stress increased significantly when the core temperature of casting reaches the liquidus temperature. stress is released when the core temperature of casting reaches 1456 ° C.At this temperature, the hot tearing susceptibility of duplex stainless steel is the largest. Reducing the core temperature to 1363 ° C, the slope of contraction stress increases, which is related to the ferrite-to-austenite transformation.