In the human lung, air is transported from the environment to the respiratory zone by conducting airways containing ~60000 airways with different scales. An accurate model of this complicated structure is crucial for studying transport phenomena in the human lung. In the present study, the parametric Lindenmayer System (L-System) has been used to produce the human bronchial tree in the bronchopulmonary segments whose shapes have been obtained based on the medical image processing techniques. The airways propagate into the host segments simultaneously similar to what happens in real life using multi-threads parallelism method. Each module in rewriting rules of the formulated L-System plays the role of an airway with its characteristic properties that have been found almost independently based on an intelligent procedure. This feature enables the method to be less sensitive to change in the host shape and size of the lungs. In addition, the stochastic behavior of the proposed procedure generates slightly different structures with the same statistical properties. Furthermore, the dimensions of the terminal branches are functions of age, which make the proposed method capable of generating the tree structure for the subjects with various ages fulfilling almost all anatomical and physiological requirements. The morphometric characteristics of the generated structure are in good agreement with the corresponding experimental data reported in the literature. The results show that the proposed method outperforms the previously reported models. The accurate three-dimensional model proposed by this study can be used for simulation of fluid distribution, mass and heat transfer, drug delivery, and particle deposition in the human respiratory system.