Polypropylene (PP) with low leakage current and high mechanical strength is a promising candidate for recyclable vacuum insulation applications, but its surface flashover voltage is low. Advantageously to widely used technologies such as fluorination and sanding, here it is shown that plasma polymerization can provide a new way to achieve higher flashover strength by depositing a bumpy coating in a two-step process using atmospheric-pressure plasma jet. The experimental results show that the suitable volume content of methyl methacrylate monomer in argon to obtain plasma polymerized coating is about 5%, and the corresponding vacuum flashover voltage is improved by 35.5%. Moreover, the morphology analysis of surface appearance shows that the PP has a bumpy surface after plasma jet deposition. The surface charge dissipation of the PP treated for 5 min is about 26% higher than that of the untreated sample, and the secondary electron emission yield decreases from 2.35 to 1.64, which can result in the surface flashover performance enhancement. This plasma-based method for depositing bumpy micropatterns is simple and may be applicable in other areas.