Platinum nanoparticles (PtNPs) and 4-aminobenzoic acid (4-ABA) were used to modify nitrogen-doped diamond-like carbon (N:DLC) film electrode by electrodeposition and cyclic voltammetry. The bare, PtNPs-, 4-ABA-, 4-ABA/PtNPs alternately-modified N:DLC film electrodes were obtained, respectively. Various analysis technologies, such as atomic force microscopy, X-ray photoelectron spectroscopy and micro-Raman spectroscopy, have been used to study surface morphology, chemical composition and bonding structure of the film electrodes. Linear sweep voltammetry and electrochemical impedance spectroscopy were performed to study the relationship between the interfacial structure of the chemically modified N:DLC film electrodes, as well as their electrochemical sensing properties toward hydrazine sulfate. Acquired results indicate that an outermost layer modified by 4-ABA or PtNPs behaved differently.