Abstract: The microstructure and mechanical properties of K438 alloy samples at different pouring temperatures were studied by means of metallographic microscope, scanning electron microscope and tensile test. The results show that when pouring temperature is 1450℃, the carbides in the alloy is mainly block and strip-like shape; when the pouring temperature is1410℃, the carbides in the alloy is mainly block-like shape. With the decrease of pouring temperature, the tensile strength and yield strength increase from 991 MPa and 922 MPa to 1006 MPa and 936 MPa, and the percentage elongation and reduction of area decrease from 5.0% and 15.3% to 4.0% and 7.5% at room temperature. When the tensile test temperature is 650℃, the tensile strength and yield strength increase from 982 MPa and 657 MPa to 1075 MPa and 849 MPa, and the percentage elongation and reduction of area decrease from 10.1% and 21.9% to 8.8% and 10.5%.