A pickup's aerodynamics characteristic for reducing drag force and increasing negative lift is studied; this study is performed to reduce fuel consumption and increase stability. The external flow devices such as a diffuser and a spoiler on the model which can change the direction of the airflow around the pickup to the desired direction are utilized. A diffuser at the rear end of the pick-up is studied to examine the effect of change of its length and angle on the aerodynamics characteristic of the Pickup. A spoiler length at the roof of the pickup spoiler as well as the change of its angle and the double spoiler are investigated; besides, the effect of the Bump's height on the tailgate of the pickup is studied. As a result of adding these devices to the pickup, increasing the diffuser length and angle, the drag coefficient and negative lift coefficient increase. In addition, the drag coefficient and negative lift coefficient will decrease if the spoiler length is increased. But with increasing double spoiler angle, the drag coefficient and negative lift coefficient increase. finally the drag coefficient and negative lift coefficient decrease with the addition of bumps on the tailgate of the Pickup truck.