Polyimide-laser-engraved porous graphene (LEPG) has emerged as a promising electrode modification material for flexible electrochemical sensing due to its low cost and high efficiency in preparation. A flexible, miniaturized, and multi-patterned electrode was fabricated using a novel and simple direct laser engraving method. Porous 3D LEPG was selectively decorated with Pt nanoparticles (Pt NPs) by in situ electrochemical deposition, resulting in Pt-LEPG with a porous network structure, which exhibited excellent sensitivity (575.75 μA mM -1 cm -2 ) and a wide range of linear response (0.01-29 nM) as a H2O2 sensor. A glucose biosensor was subsequently constructed by immobilizing glucose oxidases (GOD) onto the Pt-LEPG electrode, exhibiting a low limit of detection (0.3 μM, S/N = 3), high sensitivity (241.82 μA mM -1 cm -2 ), and a wide range of linear response (0.01-31.5 mM) under near-neutral pH conditions. The sensor was able to detect glucose in real human serum specimens with satisfactory results. The direct laser engraving on flexible PI film is a low-cost and high-efficiency methodology to fabricate LEPG with a unique porous network structure, which has great potential in flexible and wearable electronic devices for energy storage and sensing.