The severe tropical storm No. 0604 (Bilis) lands again on Beibi village of Xiapu, Fujian Province at 1250 LST 14 July 2006. It causes heavy rainfall in Fujian Province due to the interaction between the severe tropical storm and the South China Sea monsoon surge. The three-dimensional wind fields are retrieved from Xiamen and Longyan Doppler radar data using dual-Doppler radar wind retrieval technology. The 3D structure of the mesoscale convective system producing the most severe heavy rainfall at Changtai and Zhangzhou is analyzed with dual-Doppler radar retrieved wind and radar reflectivity observed by Xiamen Doppler radar. The dual-Doppler radar retrieved wind fields indicate that the SW-NE oriented mesoscale convergence lines at the lower and middle levels play an important role in the heavy rainfall. The convergence line is an important kinematic mechanism for the moisture transportation. It is quite important for the formation, breakout and maintenance of the heavy rainfall too. In the formation stage of the heavy rainfall, the convergence line evolves from weak to strong. On the other hand, the convergence line dissipates according as precipitation weakens.  Due to the effect of the southwest moist flow and the mesoscale convergence line, meso-γ convective cells occur frequently in the southwest of the mesoscale convective echo band. These cells move in the SW to NE direction along the convergence line. The cells develop and merge to each other quickly. These mergences make the mesoscale convective system more strong. The mesoscale convective line and the cells embedded in it produce the severe rainfall at Changtai and Zhangzhou. The 3D dynamic conceptual model of the cloud system structure of the heavy rainfall is also proposed in this paper.