Abstract: Differentiating integrating systems composed of differentiating monitor and integrator are often used to measure short pulsed voltage and current in pulse power facilities and accelerators.This paper describes that the passive RC integrator can lead to flat-top drop and baseline deviation when it is used to integrate a single-pulse or multi-pulse differentiating signal. According to the equivalent circuit, the formulas which describe the quantitative relationships between the RC integrator and pulse signal parameters are deduced. Flat-top drop and baseline deviation ratio are calculated under different parameters.They coincide with the PSpice simulation results.The RC integrator parameters can be accurately decided according to the formulas.