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[Display omitted] • First discovery, locally π-π conjugated polyimide in TGIC enhances loss capacity. • Increasing the number of conjugated benzenes amplifies the dielectric loss. • Right amount of PPI-D highlights the comprehensive performance for PPI-D/TGIC. • PPI-D/TGIC-0.5 has the best RL min (-15.6 dB, 16.4 GHz) and EAB (3.44 GHz, 6.0 mm). • PPI-D/TGIC-0.5 has elastic modulus (1065.4 MPa) and thermal stability (295 ℃). Creatively, endowing the resin matrix with microwave absorption performance is an effective strategy to improve the comprehensive performance for microwave absorption materials and eliminate the contradiction between matrix and absorbent. Herein, a high polar epoxy resin that triglycidyl isocyanurate (TGIC) is chemically cross-linked with locally π-π conjugated polyimides (PI) to create a novel absorbing resin matrix designed for special responses in X and Ku bands. By comparing the dielectric properties and microwave absorption performance of PBI-D/TGIC (containing benzene), PNI-D/TGIC (containing naphthalene) and PPI-D/TGIC (containing perylene), their dielectric polarization loss and microwave absorption responses will be enhanced with the increase of conjugated benzene number, which is ascribed to the enhanced π-π conjugated polarization and the instantaneously reduced resistance stimulated by electromagnetic waves (EMWs). Simultaneously, the addition of an appropriate amount of PPI-D significantly enhances the microwave absorption performance, mechanical strength, and thermal stability of TGIC-based resins. When the mixing mass ratio of PPI-D to TGIC is 1:4, the obtained PPI-D/TGIC-0.5 (PPI-D: 25.23 wt%) possesses the best minimum reflection loss (RL min) as −15.6 dB (16.4 GHz, 3.0 mm) and −8.6 dB (8.2 GHz, 4.0 mm), which is three times higher than the RL min of TGIC. Especially, the effective absorption bandwidth (EAB < -10 dB) of PPI-D/TGIC-0.5 resin can reach up to 3.44 GHz (6.0 mm) and 2.88 GHz (3.0 mm), breaking the limitations of conventional resins. Additionally, PPI-D/TGIC-0.5 resin exhibits excellent compression performance (37 MPa), elastic modulus (1065.4 MPa) and thermal stability (T 10wt.% =295 ℃). PPI-D/TGIC-0.5 resin is a strong candidate for the ideal absorbing resin matrix and holds significant potential in the applications for microwave absorption materials. [ABSTRACT FROM AUTHOR]