A green and efficient solid acid catalyst was developed for direct conversion of Jatropha oil into biodiesel over Ni modified phosphomolybdic acid (HPMo)/carbon nanotubes (CNTs) in a fixed-bed reactor. Under optimal conditions (Temperature = 330 degrees C, Pressure = 3 MPa, H-2/oil (v/v) = 800 N m(3) m(-3), Liquid hourly space velocity = 1 h(-1) ), the yield of biodiesel (C15-C18 alkanes) was 86.7 wt%, and the conversion was 98.2%. The conversion was 86.1% during five runs of recycling. Comparing with the thermal cracking process, the catalytic cracking exhibited the same performance at a lower temperature. A possible reaction pathway to the reaction was suggested.