The invention provides an electricity discharging and converting system before emission of a lithium battery for an aircraft and an electricity discharging and converting control method adopting the same, relating to the field of discharging of lithium battery of the aircraft and aiming at solving the problem of voltage lagging of the lithium battery after the lithium battery is used directly before emission of the lithium battery of the existing aircraft. The control method comprises the following steps: firstly, controlling a control switch to be turned off by a control computer, enabling an electricity discharging circuit combination, the control computer and the lithium battery to form a closed loop, and enabling the lithium battery to be pre-charged; secondly, acquiring and treating an electrical signal of the lithium battery in real time by the control computer through the electricity discharging circuit combination, comparing the pre-discharged voltage value of the lithium battery with the calibrated electricity converting voltage value, wherein the pre-discharged voltage value of the lithium battery is more than or equal to the calibrated electricity converting voltage value, controlling the lithium battery to perform electricity conversion by the control computer, thereby realizing electricity discharging and converting control to the lithium battery. The system and the control method are mainly applied to the aircraft.