During hot embossing process of polymer MEMS devices, the parameters such as temperature, pressure and time are important for the duplication precision of patterns. In this work, a novel method of hot embossing lithography for replication of multiple nano bar structure mould was conducted. The effects of hot embossing temperature and pressure on fabrication precision were studied. Linewidth of the pattern on the mould is from 71nm to 980nm. The replicas of nano bar structure were fabricated on the PMMA (polymer methyl methacrylate) layer with silicon substrate. The effects of hot embossing and demoulding temperature on replicating quality were also discussed. Experimental results indicate that higher demoulding temperature help to lessen PMMA leftover and improve the duplication quality. The hot embossing and dmoulding temperature of 110°C～120°C and 60°C～70°C were obtained to produce high quality duplication of multiple nano bar structures. Micro-grating replicas were also fabricated and demonstrated in this paper.