NOVELTY - Pretreating fluid catalytic cracking (FCC) by mild hydrocracking comprises: carrying out a mild hydrocracking operated under a pressure of 20-120 bars and at 300-500 degrees C on a hydrocarbon charge comprising a petroleum charge comprising a vacuum distillate cut and/or a deasphalted oil, and a filler of biological origin comprising components of vegetable oil and/or animal fat, to produce diesel and an effluent having an initial boiling point of greater than 330 degrees C under simulated distillation; and carrying out FCC of a composition having the effluent.    USE - The process is useful for pretreating the fluid catalytic cracking by mild hydrocracking.    ADVANTAGE - The process: increases the amount of diesel production; improves the quality of diesel product; maintains the amount of sulfur in the FCC; improves other properties of FCC (e.g. density, nitrogen content and/or hydrogen content), is cost effective.    DETAILED DESCRIPTION - Pretreating fluid catalytic cracking (FCC) by mild hydrocracking comprises: carrying out a mild hydrocracking operated under a pressure of 20-120 bars and at a temperature of 300-500 degrees C on a hydrocarbon charge comprising a petroleum charge comprising a vacuum distillate cut and/or a deasphalted oil, of which at least 85 wt% boils above 370 degrees C, and a filler of biological origin comprising components of vegetable oil and/or animal fat, to produce diesel and an effluent having an initial boiling point of greater than 330 degrees C under simulated distillation according to ASTM D2887; and carrying out FCC of a composition having the effluent. An INDEPENDENT CLAIM is included for an installation for carrying out the pretreatment process of FCC charge by mild hydrocracking with a petroleum charge comprising vacuum distillate and/or deasphalted oil, comprising a mild hydrocracking area (7) containing a catalyst and provided with a pipe (5) for the introduction of hydrogen, a pipe (6) for the introduction of the petroleum charge which is a vacuum distillate and/or deasphalted oil of which 85 wt% boils above 370 degrees C, and a pipe for the introduction of a biological filler and vegetable oil or animal fat, and a pipe (8) for evacuation of the effluent, a separation area (9) provided with a pipe for introducing the effluent and at least one pipe for the evacuation of a cut having an initial boiling point of greater than 330 degrees C, and a pipe for separating a cut of which the distillation is carried out at 130-390 degrees C, a catalytic cracking area (FCC) equipped with a pipe for introducing the cut to initial boiling point of greater than 330 degrees C, at least one pipe for the output of a light cycle oil (LCO) and at least one pipe for the release of hydrogenated castor oil (HCO), comprising, in downstream of the separation area (9), a unit of treatment and separation of the carbon monoxide present in the vapor phase of the effluent, for implementing the process.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic representation of the process for pretreating fluid catalytic cracking by mild hydrocracking.    Pipe for the introduction of hydrogen (5)    Pipe for the introduction of the petroleum charge (6)    Mild hydrocracking area (7)    Pipe for evacuation of the effluent (8)    Separation area. (9)