Manufacturing technology of high-rigidity low-stress gray iron HT300 was presented.A T-type lathe bedway sample was designed,and the T-type bedway samples and the lathe body castings of horizontal machining center were made using this new manufacturing technology and the traditional manufacturing process.Detection of physical and chemical index,test of residual stress and measurement of rail straightness were done.The key production technology of gray iron HT300 lathe body casting that has high precision of retention was studied.Results show that it is an effective approach to obtain high tensile strength(≥ 300 MPa),high elasticity modulus(≥ 120 GPa)and low residual stress(≤ 20 MPa)HT300 gray iron by 0.5-0.7%Cu,0.2-0.3%Cr,0.035-0.05%Sn compound alloying and “multi-step temperature rising/falling” heat aging under higher carbon equivalent(3.7-3.8%)condition and lower shakeout temperature(≤ 250 ℃).After a year,the deformation of 1 # and 2 # T-type lathe bedway samples is 24.5 μm and 22.1 μm,respectively,and the latter is 9.8%smaller than the former.Relatively,the low carbon equivalent high strength 1# lathe body casting,the high carbon equivalent high strength and low stress 2# lathe body casting have smaller guideway deformation,higher precision and precision retaining ability.