To find and develop an alternative energy is a major issue to our environment due to the depletion of fossil fuel. Among many kinds of alternative energies, biodiesel can be directly applied to nowadays diesel engines with benefits of low pollutions, high environmental friendliness and sustainability. Thus,biodiesel becomes one of the most promising alternative energy. Waste cooking oil, which is one of thebest oil sources for biodiesel, will cause problems when conducting transesterification due to its high free fatty acids (FFAs) content. Therefore, a pretreatment of waste cooking oil might be needed to achieve high efficiency biodiesel production from waste cooking oil. For example, an esterification step may be employed to reduce FAAs content and then transesterification is conducted to convert triglyceride into biodiesel. A common homogeneous catalyst, such as sulfuric acid, is excellent for esterification, but the homogeneous catalyst usually remains in the products, causing a negative effect on the subsequent transesterification reaction. As a consequence, more attentions have been paid on the development of heterogeneous catalysts since they have high catalytic activity, can be easier to separate, and possess the potential for repeated uses. The purpose of this research is thus to develop a two-step process to produce biodiesel, combining sequential esterification and transesterification steps, which are catalyzed by selfmade magnetic solid acid catalyst and liquid alkaline catalyst, respectively. In the meantime, the best operating conditions for this two-step process was optimized based on the operation cost