Abstract: The definition, characteristics and mathematical model of pseudo-stochastic pulses utilized in reduced-dynamic orbit determination are systematically analyzed. With the help of the real onboard GPS observations from spaceborne receiver on CHAMP satellite, the stochastic pulses are estimated with different force models and observations of different types, and the variation of stochastic pulses in different cases and adjust impact of pulses on orbit accuracy are analyzed in detail. The results show that the sizes of stochastic pulses mainly depends on the force models, whether estimating experience parameters or not and accuracy of observations used. In the cases of relatively big model errors, the set of stochastic pulses can efficiently compensate or absorb the impacts of model errors, so the orbit accuracy can be improved accordingly.