【Objective】The aim of this study was to understand the rooting mechanism of Hibiscus syriacus cuttings, including the relevant effects of two plant growth regulators and their suitable formula, as well as to improve the rooting rate and provide a theoretical support for the propagation of H. syriacus cuttings. 【Method】One-year-old branches of H. syriacus seedlings were collected as experimental materials. A completely randomized block design with two factors, including two plant growth regulators (naphthylacetic acid, NAA; indolebutyric acid, IBA) at three concentrations (100, 300 and 600 mg/L), were used. One water-treated sample was used as a control (CK). The anatomical structure, rooting growth characteristics, and leaf physiological characteristics of H. syriacus cuttings were measured during the rooting process using a UY203i biological fluorescence microscope, a STD4800 scanner calibrated for an image analysis with WinRHIZO software, a JA5003N one-thousandth electronic balance, a STYS-1 plant chlorophyll measuring instrument in vivo, and a FS-3080H photosynthesis system. The measured indexes included the rooting rate (RR), root fresh weight (RFW), root TTC reducing ability (RA), root TTC reducing amount (TTC_RA), average root length (ARL), root average diameter (RAD), root surface area (SA), root volume (RV), root tip number(RT), root length density (RLD), specific root length (SRL), chlorophyll content (Chl) and net photosynthetic rate (P_n) in the rooting process. 【Result】① It was found by microscopic observation that the adventitious root primordium of H. syriacus cuttings originated from a group of parenchyma cells with a blunt conical shape located in the cross region of pith rays and vascular cambium. The adventitious root primordia developed into young adventitious roots and then extended outward through the lenticels. ② Compared with the control (CK), the rooting rate (RR), root fresh weight (RFW), root TTC reducing ability (RA), root TTC reducing amount (TTC_RA), average root length (ARL), root average diameter (RAD), root surface area (SA), root volume (RV), root tip number (RT), and root length density (RLD) of 300 mg/L IBA treatment increased by 554%, 527%, 58%, 892%, 198%, 50%, 282%, 457%, 126% and 198%, respectively, and its specific root length (SRL), chlorophyll content (Chl), and net photosynthetic rate (P_n) were reduced by 52%, 51% and 82%, respectively. ③ According to the correlation analysis, the Chl and P_n of H. syriacus seedlings had a negative relationship with most of the root indicators. Chl was significantly negatively correlated with SA and very significantly negatively correlated with ARL and RLD. P_n was very significantly negatively correlated with RA and significantly negatively correlated with ARL and RLD. ④ Using the subordinate function value method that the rooting ability of the IBA treatment exceeded that of the NAA treatment, and the rooting ability of the 300 mg/L IBA treatment was the best. 【Conclusion】 The cortex rooting type was the main type of rooting found in H. syriacus cuttings. There was a competitive relationship between the overground parts and the underground parts of H. syriacus cuttings during the rooting process. Two plant growth regulators could promote rooting of H. syriacus cuttings and inhibit the physiological characteristics of its overground parts. The treatment with 300 mg/L IBA provided the most suitable formula.