Melt electrospinning is a safe and simple technique for the production of micro and nanofibers which can be an alternative to conventional solvent electrospinning. The effects of various melt-electrospinning parameters, including molecular weight, electric field strength, flow rate and temperature on the morphology, and fiber diameter of polylactic acid nanofibers were studied. An orthogonal design was used to examine process parameters. It was shown that molecular weight was the predominant factor in determining the obtainable fiber diameter of the collected fibers and is the most effective parameter on the average fiber diameter of melt electrospun PLA nanofibers. The flow rate has the less important impact. Mean fiber diameter (MFD) increased by increasing MW and flow rate, but decreased by increasing electric field strength and temperature. MFD of optimized fibers was below 100nm and the result of statistical analysis using Design Expert software was in good agreement with the experimental condition.