Hydrothermal liquefaction (HTL) has been proved to be an efficient method to disrupt cell walls and extract lipids from oleaginous yeast. However, many steps are needed for converting bio-oil into fatty acid methyl esters after HTL. Herein, acidic ionic liquid 1-butyl-3-methylimidazolium hydrogen sulfate ([Bmim][HSO4]) was introduced as the catalyst in HTL to convert oleaginous yeast Rhodosporidium toruloides to biodiesel in one step. [Bmim][HSO4] has dual effects on cell wall disruption and transesterification in reactions. As a result, the biodiesel yield achieved as high as 15.1 ± 3.2 % in optimal condition. The biodiesel was composed of long chain fatty acid methyl esters, and the higher heating value was 40.62 ± 0.05 MJ·kg−1. After the catalyst recycled 4 times, the catalytic efficiency still kept at 62.8 ± 2.1 %. The results indicated catalytic HTL was a direct and efficient method for biodiesel production from Rhodosporidium toruloides.