It is challenging to apply the receiver function method to teleseisms recorded by ocean bottom seismographs (OBS) due to a specific working environment that differs from land stations. Tele-seismic incident waveforms reaching the vicinity beneath stations are contaminated by multiple reflections generated by seawater and sediments and noise resulting from currents. Furthermore, inadequate coupling between OBS and seabed reduces the signal-to-noise ratio (SNR) of seismograms, leading to poor quality of extracted receiver functions or even wrong deconvolution results. For instance, the poor results cause strong ambiguities regarding Moho depth. This study uses numerical modelling to analyze the influences of multiple reflections generated by seawater and sediments on H-kappa stacking and neighborhood algorithm. Numerical modellings show that seawater multiple reflections are mixed with coda waves of direct P-wave and slightly impact extracted receiver functions, thus can be ignored in subsequent inversion processing. However, synthetic seismograms have strong responses to the sediments. Compared to waveforms of horizontal and vertical components, sedimentary responses are too strong to identify the converted waves clearly. The extracted RFs correspond to the above influences, resulting in divergent results of H-kappa stacking (i.e., Moho depth and crustal average VP/VS ratio are unstable and have great uncertainties). Fortunately, waveform inversion approaches (e.g., neighborhood algorithm) is available and valid for obtaining S-wave velocity structure of the crust-upper mantle beneath the station with sediments varying in thickness and velocity.