In this paper, morphology transformation laws by plasma modification on cemented carbide (YG16) surface have been studied and influence of decobalt time, decarbonization temperature, decarbonization time and carburizing time main factors on plasma modification lias been investigated. Plasma modification is consisted of Ar-H2 plasma etching and Ar-H2-CH4 plasma decarburizing, experiments have been done on direct current plasma spraying CVD device. On this base, influence of plating Ni-P, Ni-P-WC and Ni-P-diamond intermediate transit layer on the quality of diamond film deposited on cemented carbide(YG 6) siuface has been discussed elementally.Results have shown:1. After chemical acid etching decobalt on cemented carbide(YG 16) surface, there are more pores and serious porosity and WC particles is obviously bare under the certain depth of cemented carbide surface and sub-surface layer of cemented carbide(YG 16) surface, Co content is less of 0.5wt% under the certain depth of outer siuface layer and sub-surface layer.2. After the treatment of Ar-H2 plasma etching decarbonization on cemented carbide(YGl 6) surface by acid etching decobalt, WC of outer surface layer transform into pure W. Grains are refined obviously. Testing result of grain average size is 100nm.3. After the composite treatment of Ar-H2 plasma etching decarbonization and Ar-H2-CH4 plasma decarbonization on cemented carbide(YG16) (WC particle average size is 3 m) surface by acid etching decolcult with different time ,WC particle is refined obviously and the testing result of WC grain average size is quite a few of 10nm. On the condition of decarbonization temperature(800 癈 or so),longer decarbonization and carburizing time, inner Co atom is enriched, refined and speroidized by diffusing and evaporating into the surface space on the sample by the treatment of acid etching decobalt 20min.on tlie process of plasma decarbonization and introducing, acid etching decobalt time and plasma modification temperature are two important factors, which have apparent influence on the effect of cemented carbide(YGl 6) surface modification.4. The pretreatment of cemented carbide(YG16) blade surface without decobalt lias significant influence on nucleation density, growth velocity and crystallization quality.5. Chemical plating Ni-P and Ni-P-WC intermediate transit layer on cemented carbide(YGl 6) blade surface without decobalt has disadvantageous influence on Ihe quality of diamond film deposited.