MoS2-GO composites were fabricated by an ultrasonication method at room temperature. Raman spectra, emission scanning electron microscopy (SEM), and transmission electron microscopy (TEM) images were used to study the structural characteristics, morphologies, and sizes of the synthesized materials. An MoS2-GO/SPE (screen-printed electrode) was prepared by a facile dropping method and acted as an effective electrochemical sensor toward clenbuterol (CLB) and 4-nitrophenol (4-NP) detection. Based on the obtained results, the influence of analyte molecular structure on the adsorption ability and electronic interoperability between the targeted analyte and electrode surface were investigated in detail and discussed as well, through some electrochemical kinetic parameters (electron/proton-transfer number, electron transfer rate constant (ks), charge transfer coefficient, and adsorption capacity (Γ)). In particular, it should be stressed that 4-NP molecules possess a simple molecular structure with many positive effects (electronic, conjugation, and small steric effects) and flexible functional groups, resulting in fast electron transport/charge diffusion and effective adsorption process as well as strong interactions with the electrode surface. Therefore, 4-NP molecules have been facilitated better in electrochemical reactions at the electrode surface and electrode-electrolyte interfaces, leading to improved current response and electrochemical sensing performance, compared with those of CLB.