Abstract: The rolling tests of low alloy structural steel for building were carried out at different temperatures. The effects of rolling at different temperatures on the microstructure and mechanical properties of the low-alloy structural steel used in building were studied by means of metallographic microscope, hardness test, tensile test and impact test. The results show that the microstructure of the test steel rolled at 780℃ is polygonal ferrite and a small amount of bainite, and ferrite is elongated along the rolling direction. The 860℃ rolling test steel has uniform fine granilar bainite structure. The test steel rolled at 940℃has lath bainite structure. At 680-940℃, with the increase of rolling temperature, the hardness and tensile strength of the sample steel increase gradually, the yield strength and yield ratio increase first and then decrease and increase again, and the impact absorption energy decreases first and then increases. The yield strength and tensile strength of the test steel rolled at 860 ℃ are 631 MPa and 886 MPa, the yield ratio is 0.71, the hardness and impact absorption energy are 263.4 HV and 103 J,respectively. The comprehensive properties match well.