NOVELTY - Preparing biological diesel oil, comprises: (i) preparing insect oil comprising adding the solvent after drying and crushing the larva or pupa of complete metamorphosis, leaching and extracting, filtering, obtaining the insect oil after recycling solvent from the filtrate, pre-esterifying, then adding acidic catalyst; (ii) ester exchanging comprising subjecting the insect oil and methanol or ethanol to ester exchange reaction, adding the alkaline catalyst; (iii) optionally splitting phase; and (iv) refining and separating out the biological diesel oil by molecular distillation.    USE - The method is useful for preparing a biological diesel oil.    ADVANTAGE - The method: utilizes a wide raw material source; can be carried out in a easy manner; has low production cost; provides a novel technical route for producing the biological diesel oil and for developing and utilizing insects.    DETAILED DESCRIPTION - Preparing biological diesel oil, comprises: (i) preparing insect oil comprising adding the solvent that is 1-10 folds of weight after drying and crushing the larva or pupa of complete metamorphosis, leaching and extracting for 1-48 hours at room temperature, filtering, obtaining the insect oil with low acidic value of not greater than 2 or the insect oil with high acidic value of more than 2 after recycling solvent from the filtrate, pre-esterifying when the acidic value of the obtained insect oil is not greater than 2 and where the molar ratio of the insect oil with acidic value of more than 2 to the methanol or ethanol is 1:6-1:13, and then adding acidic catalyst that is 0.5-5% of the weight of the insect oil at 40-90 degrees C for 0.5-4 hours, where the solvent is lipophilic and/or hydrophilic organic solvents; (ii) ester exchanging comprising subjecting the insect oil with low acidic value and methanol or ethanol to ester exchange reaction, where the molar ratio of the insect oil with low acidic value to methanol or ethanol is 1:4-1:9, adding the alkaline catalyst that is 0.5-2.5% of the weight of insect oil at 40-90 degrees C for 10-60 minutes; (iii) optionally splitting phase comprising allowing the reactants to stand and layering it after the completion of the ester exchange, where the supernatant liquid is rough ester; and (iv) refining comprising adding adsorbent (1-10%), heating to 30-100 degrees C, agitating, filtering after washing the supernatant liquid obtained in the step (iii) with hot water to obtain a filtrate that is a biological diesel oil or refining the supernatant liquid obtained by the reaction in the step (iii) by using molecular distillation technology comprising two-stage treatment (a) separating the glycerol and methanol or ethanol from the reactants by molecular distillation, where the vacuum degree is 100-10Pa, the distilling temperature is 80-160 degrees C, (b) separating out the biological diesel oil by molecular distillation, where the vacuum degree is 10-0.1 Pa, the distilling temperature is 100-200 degrees C; or comprising three stages (ia) separating the methanol or ethanol by molecular distillation, where the vacuum degree is 5000-100 Pa, the distilling temperature is 60-150 degrees C, and (ib) separating the glycerol by molecular distillation, where the vacuum degree is 100-10 Pa, the distilling temperature is 100-200 degrees C, and (ic) separating the biological diesel oil by molecular distillation, where the vacuum degree is 10-0.1 Pa, the distilling temperature is 100-200 degrees C. An INDEPENDENT CLAIM is also included for the biological diesel oil prepared by the above mentioned method.