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Based on the turbulent convection model (TCM), we investigate chemical mixingin the bottom overshooting region of the convective envelope ofintermediate-mass stars, focusing on its influence on the formation andextension of blue loops in the Hertzsprung-Russell (HR) diagram. A diffusivemixing model is adopted during the Red Giant Branch (RGB) phase. The propertiesof the blue loop are changed by modification of the element profiles above theH-burning shell, which results from the incomplete mixing in the bottomovershooting region when stellar model evolves up along the RGB. Suchmodification of the element profiles will lead to an increase of the opacity inthe region just above the H-burning shell and a decrease of the opacity in theouter homogeneous convection zone, which will result in a quick decrease of theH-shell nuclear luminosity $L_{H}$ when the stellar model evolves from the RGBtip to its bottom and, finally, a much weaker and smaller convection zone willbe obtained in the stellar envelope. This helps to form a longer blue loop. Theextension of the blue loop is very sensitive to the parameters $(C_{X}$ and$\alpha_{TCM})$ of the diffusive mixing model and of the TCM. The resultsmainly show that: 1) comparing to the results of the classical model with themixing-length theory, the lengths of the obtained blue loops with differentcombinations of the values of $C_{X}$ and $\alpha_{TCM}$ are all increased andthe length of the blue loop increases with the values of parameters  $C_{X}$ and $\alpha_{TCM}$; 2) the diffusive mixing model can significantlyextend the time of stellar models lingering on the blue side of the HR diagram,even though the length of the blue loop for the 7$M_{\odot}$ star has a lessprominent difference between the classical and diffusive mixing model;

Chemical mixing by turbulent convection in the overshooting region below the convective envelope of RGB stars