The ultra-precision turning performance of electroless nickel-coated mandrels which are used for the replication of X-ray mirrors. Effects of single-point diamond turning parameters such as depth of cut, spindle speed, and feed rate on the surface roughness are studied. The experimental results show that the feed rate has a significant influence on the surface roughness, while the spindle speed and depth of cut have no obvious influence on it. The process experiment of NiP alloy ultra-precision turning was carried out, the optimized process parameters of cutting depth, spindle speed and feed rate were obtained, and the surface roughness prediction model was established. The optimized process parameters were applied on manufacturing of electroless nickel-coated mandrels with diameter of 110 mm and length of 140 mm. The mandrel has been successfully machined to about PV61.37-83.47 nm, RMS7.952-10.326 nm, Ra6.379-8.332 nm, roundness 0.39 μm, slope error of the profile 0.42 μm. The above results meet the manufacturing requirements of the X-ray mirrors, which prepares the technical storage for manufacturing of larger X-ray mirrors.