The invention discloses an integral pipe body cutting and stacking mechanism for a car. The integral pipe body cutting and stacking mechanism comprises a cutting mechanism, a transferring mechanism and a stacking mechanism. The cutting mechanism is used for cutting straight pipes to be cut. The transferring mechanism is used for conveying the cut straight pipes to the stacking mechanism to be stacked. The cutting mechanism comprises a first conveying device, a straight pipe aligning and blanking device, a rotary feeding device, a cutting machine, a second conveying device and a leftover material separating device. The invention further discloses a method for using the integral pipe body cutting and stacking mechanism for the car to cut and stack pipe bodies for the car. The integral pipe body cutting and stacking mechanism has the beneficial effects that the cutting efficiency is improved, the cutting precision is high, cut leftover materials can be separated conveniently, and the straight pipes can be stacked conveniently.