In the present experimental work, the friction stir welding was performed on AZ31B magnesium alloy. Four process parameters selected for the optimization of were rotational speed, weld speed, plunge depth and tool shape. Taguchi method was used to design the set of experiment that were carried out for the optimization of welding. Aforementioned four parameters, at four level each and L16 orthogonal array was used. The response characteristics selected was ultimate tensile strength and Taguchi's larger is better approach was used for calculating signal to noise ratio. The experiments were carried out according the Taguchi design of experiment made in Minitab 17 Software. Using signal to noise ratio, the optimum level of each parameter was found. Signal to noise ratio indicate the most influencing parameter for optimum tensile strength was weld Speed followed by plunge Depth and rotational Speed. The tool Pin profile has the least effect on the response characteristics. The effect of all these parameters on the tensile strength was validated by the ANOVA. Further, the contribution of each parameter was found by using ANOVA.