Abstract: In this paper, some coordinate systems used in analysing the dropcapsule motion are buiIt, the mathematical model used in solving the parameters of attitude motion is given. According to the physical background of micro-g acceleration in the dropcapsule, mathematical description and physical explaination of micro-g environment are presented, the expression of micro-g acceleration at arbitrary point in the dropcapsule is led out. This paper points out that the major factors influencing the level of micro-g are aerodynamic drag and attitude motion. Lastly, the levels of micro-g in the dropcapsule are analysed and estimated, the numerical calculations are carried out for micro-g acceleration generated by the drag. The calculation results show that the dropcapsule released from the-height of 30 km and above will provide up to 30-40 seconds of micro-g time with g-levels of <5×10^-2g.