Long fiber thermoplastic pellets (LFTP) are composite materials that consist of thermoplastic and discontinuous reinforcement fibers with an aspect ratio more than critical aspect ratio. LFTP are high modulus, high strength and excellent impact resistance. Normally, commercial LFTP were produced by hot melt impregnation process or combinding between pultrusion and extrusion process. In this research, Thermoplastic pultrusion process was used for production of LFTP. The thermoplastic pultrusion process is uncomplicated process and machine less than hot melt impregnation process. The glass fibers were used in LFTP as a reinforcement and polypropylene (PP) fibers were used as a matrix of LFTP. General full factorial design of experiment was used to determine the optimal condition for un-impregnation on specimen from pultrusion process of LFTP. The study focused on three factors including the filling ratio, the molding temperature and pulling speed. The specimens were investigated on impregnation of resin in LFTP by microscope. The results show that un-impregnation decreased with an increase of filling ratio. Un-impregnation decreased with an increase of molding temperature. Finally, un-impregnation had increased with an increase of pulling speed. However, the void content has a little effect to molding temperature and pulling speed, or they have not almost effect. From statistical analysis, the optimal condition for the pultrusion process of LFTP was filling ratio of 104.73 %, molding temperature of 230 °C and pulling speed of 10 cm/min, which was given the lowest un-impregnation value of 5.85 %.