To overcome the difficulties in the fabrication of the nanoimprint mold with lin ewidth smaller than 50nm, we deposited a-Si/SiNx multilayer films in plasma enhanced chemical vapor deposition system and then prepared the relieo-n anomold on the cleaved section of the multilayer films by selectively etching or reactive ion etching process. Due to the slow deposition rate, the thickness of the sublayer, and therefore the size of the strips and grooves can be controlle d on the nanometer scale by altering deposition time. The smallest width we get by now is the 20nm strips and 20nm pitches，which is better than that fabricated by electron beam lithography.