The high modulus carbon fibre is usually used in orbiting craft due to its properties of multi-variety, small quantities and high quality. Quality control of prepreg tow for automated fibre placement(AFP) is discussed. With the help of the hot-melt impregnation winding method, the resin content of the fiber bundle under different processing parameters is analyzed. And the orthogonal experiment is designed to explore the influence degree of each factor. The result shows that: the most important influence factor is the gap between limiting roller and impregnation roller, and the winding speed, resin temperature, speed ratio, and unreeling fibre tension are successively important. The optimal combination of process parameters to prepare HS40/CY-10W high modulus carbon fibre prepreg tow is determined: The gap between two rollers is 0.15 mm, the winding speed is 12.56 m/min, the resin temperature is 100 ℃, the speed ratio is 60%, and the unreeling fibre tension is 13 N. Under the optimal combination of processing parameters, the prepred prepreg tow is stable and continuous with resin content as 34.0±1.0% and coefficient of variability equal or less than 0.79%, which can meet the requirement for AFP.