In this paper, the bag-absorbing capacity of different kinds of packaging bags by bag-absorbing devices of big wrapping machine was explored, so as to increase the successful vacuum-sucking rate and the working efficiency. Through analysis of the absorbing principle of the vacuum absorbing device, the vacuum absorbing model was built according to main influencing factors of absorption performance. The coefficient of leakage was introduced and the absorbing test was made on three kinds of wrapping bags, namely, lined woven bags, film-covered woven bags as well as paper-plastic compound bags, and the change of air pressure was recorded. The experiment using the coefficient of leakage can efficiently characterize the absorption capacity and the result showed that the change of air pressure differed according to different woven bags absorbed. The leakage coefficients of 0.192, 0.089 and 0.042 were set. According to the leakage coefficients and working efficiency, the vacuum air pressure of the three kinds of wrapping bags when being absorbed should be set as 59~64 kPa, 70~75 kPa, 66~71 kPa and the successful vacuum-sucking rate was over 99%. The absorption capability parameters and reasonable vacuum-sucking parameters are obtained, which provides reference for reasonable determination of working range of air source and satisfaction of bag-adsorption response time of the vacuum device and the successful rate.