Alkaline peroxide mechanical pulp (APMP) is a newly emerging high yield pulp (HYP) with numerous advantages. However, the drawback of the alkaline peroxide mechanical pulp from untreated plant biomass is its poor network strength. In this work, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride (CHPTAC) modification was proposed to enhance pulp network strength by fiber surface modification that could enhance fiber bonding. Three factors were analyzed by response surface methodology (RSM) to optimize treatment conditions based on factorial designs. The results showed that the optimal conditions were CHPTAC dosage of 0.8% (oven-dry pulp), NaOH dosage of 0.1% (oven-dry pulp), and pulp concentration of 8%. The modified pulp fibers were characterized by elemental analysis, charge density analysis, Fourier transform infrared spectroscopy (FTIR), thermal gravity analysis (TGA), and internal bond strength analysis, as well as zero span tensile analysis. The physical strength of the modified APMP pulp was increased in terms of tensile index, tear index, and burst index. After modification, the tensile index, tear index, and burst index increased by 35.3%, 29.2%, and 16.7% respectively. The internal bonding strength increased by 144.4%; however, the increase of zero span tensile index of modified pulp fibers was insignificant.