KF/CaO nanocatalyst was prepared by using impregnation method and used to convert Chinese tallow seed oil to biodiesel. The effects of different preparation conditions on biodiesel yield were investigated and the structure of the catalyst was characterized. Transmission electron microscopy (TEM) photograph showed that the catalyst had porous structure with the particle size of 30-100 nm. Brunauer-Emmet-Teller (BET) analysis indicated that the catalyst specific surface area was 109 m(2) g (1) and average pore size was 97 nm. X-ray diffractometer (XRD) analysis demonstrated that the new crystal KCaF(3) was formed in catalyst, which enhanced catalytic ability. Under the optimal conditions, the biodiesel yield was 96.8% in the presence of as-prepared KF/CaO catalyst, showing potential applications of catalyst in biodiesel industry. (C) 2010 Elsevier Ltd. All rights reserved.