Abstract: The development of typhoon No.7504 (ORA) along the tropical convergence zone is simulated with a five-level primitive equation model including large scale and convective condensation, surface friction, sensible and latent heat exchanges between the sea and the air. Initial wind is estimated by means of the balance equation in σ-coordinate.The asymmetrical distribution of wind and temperature is obtained. Results of experiments from different initial states show that, (1) The strong horizontal shear between east and west wind on two sides of convergence zone is uncertainly an unique condition for formation of typhoon, (2) Surface disturbance plays an important rule in process of typhoon development and, (3) The channel of moisture from large-scale environment is an important factor for initiation and development of typhoon.