An improved multi-component two-dimensional hybrid model is presented for the simulation of Trichel pulse corona discharge. The model is based on the plasma hydrodynamics and chemical models, including 12 species and 27 reactions. In addition, the photoionization and secondary electron emission effects are taken into account. Simulation is carried out on a bar-plate electrode configuration with an inter-electrode gap of 3.3 mm, the positive potential applied to the bar being 5.0 kV, the pressure in air discharge being fixed at 1.0 atm, and the gas temperature assumed to be a constant (300 K). In this paper, some key microscopic characteristics such as electric field distribution, net charge density distribution, electron density distribution at 5 different instants during a Trichel pulse are analyzed emphatically. Further more, the electron generation and disappearing rates, positive and negative ion distribution characteristics along the axis of symmetry are also investigated in detail in the later Trichel pulse cycle. The results can give valuable insights into the physical mechanism of negative corona discharge.