How to achieve synergistic improvement of permittivity (ε_r) and breakdown strength (E_b) is a huge challenge for polymer dielectrics. Here, for the first time, the π-conjugated comonomer (MHT) can simultaneously promote the ε_r and E_b of linear poly(methyl methacrylate) (PMMA) copolymers. The PMMA-based random copolymer films (P(MMA-co-MHT)), block copolymer films (PMMA-b-PMHT), and PMMA-based blend films were prepared to investigate the effects of sequential structure, phase separation structure, and modification method on dielectric and energy storage properties of PMMA-based dielectric films. As a result, the random copolymer P(MMA-co-MHT) can achieve a maximum ε_r of 5.8 at 1 kHz owing to the enhanced orientation polarization and electron polarization. Because electron injection and charge transfer are limited by the strong electrostatic attraction of π-conjugated benzophenanthrene group analyzed by the density functional theory (DFT), the discharge energy density value of P(MMA-co-PMHT) containing 1 mol% MHT units with the efficiency of 80% reaches 15.00 J cm⁻³ at 872 MV m⁻¹, which is 165% higher than that of pure PMMA. This study provides a simple and effective way to fabricate the high performance of polymer dielectrics via copolymerization with the monomer of P-type semi-conductive polymer.