Biodiesel has become more attractive recently because of its environmental benefits, and the fact that it is derived from renewable resources. Recently, the acidic oil and waste cooking oil were the main resources for the biodiesel production, due to the economical and environmental consideration. However, the product obtained from the transesterification with dark colour. Activated carbon (ACN), activated clay (ACY), activated bleaching earth (ABE), attapulgite (ATE) were employed to refine the undecolored biodiesel. Among all studied decolorants, activated clay exhibited higher activity and more economically competitive. In addition, decoloring process of undecolored biodiesel by activated clay was performed; the optimum conditions were obtained as decoloring temperature 60°C, time 60 min and dosage of activated clay 3 wt. % at atmospheric pressure. Besides, the water content of biodiesel should be below 1 wt. % while ACY was used as decolorant. This paper compared contents and features of decolorization by ACY and rectification under vacuum. The results indicated that higher decolorization ratio(DR) and better quality product will be achieved through rectification, while the decolorization by ACY method should be an proper choice if the biodiesel solded by mixing with diesel fuel.