Objective To study the absorption mechanism and improve the bioavailability of ambroxol hydrochloride (AMB) across the Caco-2 cell monolayer model. Methods The integrity and functionality of the Caco-2 cell monolayer model were analyzed by the transepithelial electrical resistance (TEER), the apparent permeability coefficient (Papp ) of acyclovir and the efflux ratio (ER) of rhodamine 123. The effects of drug concentration, drug-drug interaction and pH on the P_app(AP→BL) and ER of AMB were investigated using the Caco-2 cell monolayer model. Results The TEER values of all the permeation experiments were above 200 Ω·cm2 . The P_app(AP→BL) of acyclovir was less than 1×10^-6 cm/ s. Furthermore, the ER of rhodamine 123 was lower than 2, indicating that the Caco-2 monolayer model was successfully established in this experiment. Compared with the high permeability control group, the P_app(AP→BL) was significantly decreased in the low-dose AMB group, but the ER was not affected. There was also no difference in the ER between AMB used alone and in combination with METO; however, there was a significant increase in the P_app(AP→BL) in the monotreatment group. Furthermore, the P_app(AP→BL) of AMB transport under pH 6. 5 showed a significant difference compared with that under pH 7. 4 and 8. 0 (P< 0. 01). Conclusions The transport of AMB across the Caco-2 cell monolayer model was facilitated by diffusion, and combination therapy was not conducive to AMB absorption. However, an alkaline environment accelerated AMB absorption.