Pressurized catalytic co-pyrolysis offers a promising route for converting oxygen-rich biomass residues and aromatic plastic waste into hydrocarbon-rich liquid fuels. However, the pressure-dependent catalytic conversion behavior of medicinal biomass residue (MBR) and polystyrene (PS), particularly its relationship with reaction kinetics, gas evolution, and oil quality, remains insufficiently clarified. In this study, MBR and PS were co-pyrolyzed under nitrogen in a pressurized fixed-bed reactor using Fe–Mo/ZSM-5 as a bifunctional catalyst. The effects of temperature, pressure, and feedstock ratio were evaluated through product distribution, gas composition, liquid-phase analysis, catalyst characterization, and isoconversional kinetic modelling. Kinetic analysis over α = 0.2–0.8 showed that Fe–Mo/ZSM-5 reduced the average apparent activation energy from 190.27 to 163.23 kJ mol-1 by FWO and from 178.30 to 155.45 kJ mol-1 by KAS, confirming the catalytic promotion of MBR/PS decomposition. Thermodynamic analysis further indicated that the catalyst decreased the enthalpy requirement while forming a more ordered catalyst-assisted transition state. The optimum condition was obtained at 600 °C and 1.5 MPa, giving a maximum liquid yield of 63.5 wt.% and an oil lower heating value of 41.37 MJ kg-1. MBR: PS mass ratio of 1:3 provided the most favorable co-pyrolysis performance. Fe–Mo/ZSM-5 promoted hydrogen transfer, deoxygenation, and aromatization, leading to a maximum BTEX yield of 46.3%.