In order to realize molding process of polymethyl methacrylate (PMMA) micro-structured parts with high efficiency and high precision, a new molding method is presented with laser melting. This paper develops fabrication and experiment devices,and carry out the experiment of laser melting-molding on PMMA microstructures by CO2 laser scanning. According to thermal physics and energy conservation the temperature variation of samples is analyzed with the method of numerical analysis and simulation, and the effects of the various processing parameters on replication quality are investigated via orthogonal experiment. The results show that the temperature of the melt is the main factor affecting the quality of the molding, where high temperature leads to a good molding precision. Laser power is the decisive parameter to influence the replication precision of the micro-structure; scanning time and mould temperature are the secondary factors; molding pressure is the least important among them. At last, the molding process of PMMA microstructure with good replication precision is obtained by optimized process. It is demonstrated that the proposed process is a feasible and effective way to laser melting-molding PMMA micro-structured parts.