Vegetable oil, which can be produced from various vegetables utilizing the solar energy, is a renewable resource. Besides, it is also a good substitute of diesel. With the improvement of our living standard, waste vegetable oil is discarded largely everyday, and thus it can not only cause environmental pollution but also is a waste of energy resources. For solving these problems, this paper introduced the way and procedures of how to gain the substitute fuel of diesel using waste vegetable oil by transesterification, and the most satisfying technological parameters were obtained, so it holds the preferable value of popularization and application. The results show: 70℃ of temperatures and 1∶6 of molar ratio of oil to methanol and 1.0% of concentration of catalyzer (NaOH) and 20～30 minutes of reaction time gave the most successful results in terms of the fatty acids methyl esters, 92% of mixture can be transformed into biodiesel.