Abstract: Fiber orientation and distribution are the main factors affecting the mechanical properties of fiber reinforced PP composite. This paper presented an approach for predicting the number of fibers and each fiber's orientation. By introducing fiber orientation tensor, the average distribution of fibers in the glass fiber reinforced PP resin composite was acquired through injection molding simulation with Moldflow. Quantitative fiber distribution and orientation along thickness at specific spots were obtained by metallographic method. The proposed approached was demonstrated by a car instrument panel made from injection molding of thermoplastics with glass fibers. Tensile test samples were cut from the instrument panel with an angle of 0°, 45°, 90° to the fiber direction at sites where fibers were highly aligned. The tensile moduli were obtained through tensile tests. The fiber orientation distribution and its effect on the tensile modulus were investigated by the proposed method. It is shown that the car instrument panel is heterogeneous in mechanical properties. The fibers are roughly distributed into three layers along the thickness direction with each layer having aligned fibers.