The utility model discloses an in-vehicle ammunition feeding structure of a parallel arm system. The in-vehicle ammunition feeding structure comprises an ammunition carrier, an ammunition can, a control box, a DC drive motor, a lifter and an ammunition counter. The lifter is driven by the DC drive motor. The ammunition carrier is installed on the lifter and carries the ammunition can. The ammunition counter is connected with the control box, transmits ammunition supplementing instructions to the control box and receives initialization instructions. The control box controls the DC drive motor to drive the lifter to ascend and descend. The in-vehicle ammunition feeding structure has an ammunition counting function and can give an ammunition supplementing prompt under the condition that ammunition is not enough; the ammunition carrier is descended by controlling the lifter, afterwards, the ammunition can filled with ammunition is loaded onto the ammunition carrier and connected with ammunition loaded ammunition belts, and finally the ammunition carrier is lifted to an ammunition feeding position by controlling the lifter, so that the ammunition supplementing process is completed. According to the in-vehicle ammunition feeding structure, an arm operator can conveniently know the quantity of remaining ammunition in the ammunition can, so the situation that the military operations are hindered because the ammunition is not enough during combat is avoided; meanwhile, unnecessary casualties are reduced due to the fact that the ammunition supplementing process is completed in a vehicle cabin as well, and therefore the safety in the ammunition supplementing process is guaranteed.