The one-step synthesis of biodiesel from waste oil with high FFAs (free fatty acids) content was developed under mild condition (70 degrees C, 1 atm) using novel acidic ionic liquid immobilization on PDVB (poly divinylbenzene) as catalyst. The solid acid owns high activities for both the esterification of FFAs and transesterification of triglyceride with total yield over 99.0%. The novel solid acid combined the high activities of acidic ionic liquids and the easy separation of solid catalysts. The mild reaction conditions, high catalytic activities, high total yield, reusability and high stability were the key properties of the novel methodology, which would greatly reduce the production cost for the industrial application. (C) 2013 Elsevier Ltd. All rights reserved.