Abstract: An optimal scheme was found by comparison of two results obtained separately from X-ray diffraction and SEM methods.The 4-storke engine oil is used as test lubricant.Cu nano-particles were used as additive dispersed into ordinary oils with different weight proportion and nano-particles' antiwear and reducing friction performance is compared with traditional oil.The results indicated that Cu nano-particle has antiwear and friction-reducing properties better than the traditional oil.It will be a new lubricant.