A beamstop is commonly used in coherent diffractive imaging (CDI) experiments to collect more high-angle diffraction signals. But it causes the low-frequency signals missed, which can make CDI reconstruction unstable or even fail. In this work, a systematic simulation investigation of the effects of the missing low-frequency signals on the quality of reconstructed images of ptychographic CDI (PCDI) is performed using the ptychographic iterative engine algorithm. We found that the robustness of PCDI to the beamstop is much higher than that of the plane-wave CDI, and a smaller incident probe or a larger probe overlap ratio ( 70%) can further decrease the negative influence of missing low-freqency signals on the reconstruction image. The probe scanning position error will be the main degrading factor of PCDI instead of the beamstop in the higher overlap cases, and needs to be corrected in experiments by using high precision motors or adopting the position refinement algorithms. Our results provide quantitative guidelines for the usage of beamstops in ptychographic CDI experiments.