Synthesis of biodiesel is a strategic step in overcoming energy scarcity and the environmental degradation caused by the continuous use of the petroleum based energy. Biodiesel as an alternative fuel for diesel engine is produced from renewable resources such as vegetable oils and animal fats. The main obstacle in the biodiesel production is the high price of the raw materials, resulting in the price of biodiesel is not competitive compared to the petroleum diesel. Therefore, the use of waste frying oils (WFO) is one way to reduce the cost of biodiesel production, because of its availability and low price. In the present work, WFO from California Fried chicken (CFC) restaurants in Surabaya were used as feed stock for the biodiesel production. The experiments were conducted using three steps of processes: pre-treatment of WFO, preparation of alumina based composite catalyst CaO/KI/γ-Al 2 O 3 and transesterification of treated WFO. WFO was treated by several types and various amounts of activated adsobents. The treated WFO was transesterified in three neck glass batch reactor with refluxed methanol using CaO/KI/γ-Al 2 O 3 . The results reveal that the best method for treating WFO is using 7.5% (wt. % to WFO) of coconut coir. Alumina based composite catalyst CaO/KI/γ-Al 2 O 3 was very promising for transesterification of WFO into biodiesel. The yield of biodiesel was 83% and obtained at 65ºC, 5 h of reaction time, 1:18 of molar ratio WFO to methanol and 6% amount of catalyst.