Abstract: With the continuous improvement of diesel engine power, higher and higher performance requirements are put forward for gray cast iron cylinder block materials.The microstructure and properties of low carbon equivalent (CE≤3.9%)gray iron was studied by metallographic microscope, scanning electron microscope, Brinell hardness tester, electronic universal sampler and laser thermal conductivity tester.The effects of carbon equivalent (3.2%-3.8%)on the microstructure, mechanical properties and thermal conductivity of gray cast iron were explored.The results show that when the carbon equivalent is reduced from 3.8% to 3.2%, the morphology of graphite becomes fine and curved, and the graphite length decreases; the distance between pearlite layers becomes dense and uniform, and the tensile strength reaches 385.9 MPa; with the decrease of carbon equivalent, the dependence of thermal conductivity on temperature decreases gradually.