The invention discloses a gear-shaped biodiesel catalyst and a preparation method thereof. The preparation method comprises the following steps: preparing a Ca/Al/La biodiesel catalyst with a pore structure from graphite phase-like carbon nitride (g-C3N4) as a template agent, that is, roasting melamine so as to prepare g-C3N4, dispersing CaCl2, Al(NO3).9H2O, La(NO3)3.6H2O and g-C3N4 in water, after dispersion, slowly dropping a NaOH into a mixed solution, performing continuous reaction for a certain time, performing reaction in an oven, performing suction filtration, drying, and roasting, thereby obtaining the Ca/Al/La biodiesel catalyst. The catalyst disclosed by the invention is relatively large in specific surface area, rich in active site and very high in catalysis activity and can be repeatedly used, and the use amount of the catalyst only accounts for 0.5-2% of the mass of biomass oil.