Hot embossing is a microfabrication technique for making microchannels and microfluidic devices. Temperature and pressure along with the material thermos-mechanical properties are the key parameters in controlling the shape of embossed channels. In this paper, experimental and numerical investigations of pressure and temperature effects on channel dimensions are presented. The material used as workpieces is poly methyl methacrylate (PMMA). The depth, upper width and lower width are the main dimensions of microchannel which are studied in this work. Experiments were performed at temperatures of 140, 150, 160, 170 and 180℃ and pressures of 235kPa, 295kPa and 340kPa. Numerical and experimental results show a good agreement, i.e. 6.7% difference in dimensional length in the worst case and less than 0.3% in the best case. Based on width and depth values obtained via both experiments and simulations an optimum condition of temperature and pressure is presented in this paper for forming of microchannel on PMMA. Based on performed experiments, 150°C with 295kPa is found to be the nearest condition to the optimum point.