Biodiesel that mostly comes from pure renewable resources provide an alternative fuel option for future because of limited fossil fuel resources as well as environmental concerns. The transesterification of non-edible oils for biodiesel production is one of the promising process for biodiesel production to overcome this future crises of energy. The utilization of waste frying oil into biodiesel have great worth for economization of biodiesel cost as well as the conversion of waste into value added product with environmental protection. The purpose of the present work is to optimize the process of biodiesel production over a heterogeneous clay based catalyst. Particularly, the transesterification of waste frying palm oil with methanol was studied in the presence of montmorillonite clay K-30 as solid base catalyst that have both of acid and basic nature. The observed date was then optimized with the help of Design of Experiments software. The Response Surface Methodology (RSM) based on four-variable central composite design (CCD) with α (alpha) = 2 was used for this purpose. The transesterification process variables were reaction temperature, x1 (40-140oC), reaction period, x2 (60-300 min), methanol/oil ratio, x3 (6:1- 18:1 mol/ mol) and amount of catalyst, x4 (1-5 wt). The results showed that waste frying oil is a good feedstock for biodiesel production and high yield of 78.4 was obtained during optimization of this biodiesel process that was noted after 180 min at temperature 90°C, with a 12:1molar ratio of methanol to waste frying oil and using 3wt of montmorillonite clay K-30 catalyst. © 2016 The Authors.