Taking different length sizes of medical tapes and packaging cartons as the object, the work aims to design an automatic cartoning machine which consists of box-taking mechanism, pushing mechanism, delivery mechanism, box-sealing mechanism and framework to package cartons with different lengths. On the basis of studying the traditional box-taking mechanism of planetary gear train with cylindrical gears, the box-taking mechanism of planetary gear train with cylindrical-elliptical gears was designed and optimized. Several mechanisms with regulating function to push medical tap, seal the carton and deliver the medical tap, were designed. The prototype was manufactured and adjustment of each packaging process was carried out to package two kinds of specifications tapes and cartons experimentally. The acceleration of the new box-taking mechanism was 14.3% less than that of the traditional mechanism at the point to taking or putting the carton. The velocity of the new mechanism is also reduced by 14.3% at the point of collision point between carton and obstacle. The prototype could be used for packaging materials with different length specifications. The box-taking mechanism of planetary gear train with cylindrical-elliptical gears increases the reliability of the cartoning machine. The design is reasonable and suitable for packing demand to cartons with different length sizes. It can provide reference for similar applications in packaging industry.