Abstract: To quantitatively describe the net mass of attached resin particles near the fiber-bundle outer surfaces during the powder-slurry preparation of carbon fiber reinforced polyetheretherketone (CF/PEEK) thermoplastic prepregs, a resin particle capture model based on an equivalent outer-surface capture layer was established. Based on the attachment characteristics of resin particles near the outer surfaces of the spread fiber bundle, the net attachment process of resin particles during slurry impregnation was represented by the contribution of outer-surfacecapture layers. An equivalent capture thickness β was introduced to represent the overall particle-capture capability of the fiber-bundle outer surfaces. An analytical relationship was derived to relate the prepreg resin mass fraction W_r to the slurry resin mass concentration C_m, spread-tow width W, and total fiber-bundle linear density λ. Five sets of preparation experiments with PEEK mass fractions in the slurry of ω_r = 5%–13% were used for model calibration. The results show that the constant-β model (β_mean = 463 μm) can describe the overall increase in resin mass fraction with slurry concentration. The equivalent capture thickness determined from experimental data increases with concentration, and an empirical correction with a limited-growth trend can be used to parameterize β(C_m) within the tested concentration range. Validation under different W–λ combinations shows that the relative errors of the corrected model for five validation points are 0.7%–3.7%. The dimensionless collapse analysis further shows that both calibration and validation data are distributed close to the theoretical relation W_r/(1-W_r) = 2C_m β(C_m)W/λ. The parametric contour map based on the corrected model indicates that a higher slurry concentration or a larger W/λ leads to a higher resin mass fraction, providing a quantitative reference for selecting front-end process parameters for CF/PEEK prepregs with a target resin mass fraction.