A solid base nanocatalyst was prepared by ZrO(2) loaded with C(4)H(4)O(6)HK and investigated for transesterification of soybean oil with methanol to biodiesel. The obtained nanocatalyst was characterized by means of XRD, FTIR, TEM, TGA, N(2) adsorption-desorption measurements and the Hammett indicator method. TEM photograph showed that the nanocatalyst had granular and porous structures with particle sizes of 10-40 nm. The nanocatalyst had longer lifetime and maintained sustained activity after being used for five cycles. The separate effects of the molar ratio of methanol to oil, reaction temperature, nanocatalyst amount and reaction time were investigated. The experimental results showed that a 16:1 M ratio of methanol to oil, 6.0% catalyst, 60 degrees C reaction temperature and 2.0 h reaction time gave the best results and the biodiesel yield of 98.03% was achieved. Production of biodiesel has positive impact on the utilization of agricultural and forestry products. (C) 2010 Elsevier Ltd. All rights reserved.