Abstract: Based on the operating principle and characteristics of the negative pulse downlink communication system, a managed pressure balance method with SPP as the reference and a wellbore transient flow model were established. The wellbore flow rate of the negative pulse downlink communication was analyzed, and the effectiveness of the managed pressure balance method was verified. The numerical simulation results showed: The signal propagation from the stand pipe to the wellhead during the negative pulse downlink communication, the flow rate fluctuation was significantly distorted, and the pressure fluctuation was significantly reduced, both of which had time delay effects; The variation pattern of SPP and BHP was basically consistent, proving that SPP could be used as a reference data for regulating back pressure; The negative fluctuation of BHP was decreased by 80.9% while managed pressure downlink communication, and the fluctuation pattern of bottom hole flow rate was basically consistent with that under constant wellhead backpressure conditions; The research results indicated that this method could effectively suppress the negative fluctuation of wellbore pressure during negative pulse downlink communication while drilling, maintained stable bottom hole pressure, and did not interfere with the flow signal of the negative pulse downlink communication, provided theoretical guidance for on-site operations.