Partial discharges (PDs) diagnostics are necessary to monitor and detect any abnormal conditions such as; impurities, voids or gas bubbles during the manufacturing process of insulating materials of power cables. This paper aims to enhance PD activity of polyvinyl chloride (PVC) with the insertion of chemically functionalized silicon dioxide (SiO2) nanoparticles through using the solvent compound method. The surface functionalization of SiO2 was performed using amino silane as a coupling agent after activating their surfaces with methane-sulfonic acid. After that, PVC/SiO2 nanocomposites, with different loadings of nanoparticles (0.5, 3%), were synthesized with the aid of ultra-sonication for better dispersion of nanoparticles. Then, the internal discharge measurements are performed using the traditional needle-plane configuration with the help of phase resolved partial discharge analyzer (PRPDA). This technique is used to analyze the statistical characteristics of PDs pattern with respect to the phase angle of applied voltage for all samples. It is found that the PD activity of PVC/SiO2 amino-functionalized nanocomposites samples that represented by discharge magnitude, inception voltage, extinction voltage, and the PD generation rate was enhanced compared to that of the PVC/SiO2 un-functionalized nanocomposite or neat PVC. This was explained considering the effect of SiO2 in trapping process and initial electron generation inside the insulation material. Also, governing mechanisms for positive and negative PD activity were discussed.