The potential of Calcinated shrimp shells (Cao) is a suitable heterogeneous basic catalyst for transesterification of high FFA content waste cooking oil was investigated. A transesterification process produced Biodiesel. In the first step, the waste cooking oil was Filtered and mixed in magnetic stirrer for 30 min at room temperature at 300 rpm. The esterified oil was converted into biodiesel by reacting with methanol using calcinated Shrimp shells (Cao) as a heterogeneous basic catalyst by taking 6:1 ratio of methanol and oil respectively.