The Taiwan- Luzon double volcanic chain stretches for nearly 500 km and locates between Taiwan Island and Luzon Island in a north- south direction. Its origin has not been determined. It is attributed to the subduction of light materials (mid- ocean ridge of the South China Sea or light plateau in the northern part of the South China Sea). However, numerical modeling does not effectively support this viewpoint. Along with convergence of the Eurasian- Philippine Plate, the eastern sub- basin of the South China Sea was passively subducted beneath the Philippine Plate. In order to verify the control of passive subduction and active subduction on the subduction angle, two- dimensional high- precision numerical models are constructed in this study. The influence of convergence direction on the subduction angle is investigated. The simulation results suggest that the subduction angle can change dramatically only by transferring convergence direction. Under passive subduction, low- angle subduction occurs readily if conditions are appropriate. Based on a large number of previous multidisciplinary studies, it can be determined that the conditions of the South China Sea- Philippines subduction system meet the requirements of low- angle subduction, which is manifested in two aspects: ① the age of the eastern South China Sea sub- basin decreases northward from the latest mid- ocean ridge, with the oldest of 33 Ma, less than the 40 Ma required for low- angle subduction; ② the convergence rate of Eurasian- Philippine plate is higher than 4 cm/a required by low- angle subduction. Therefore, this study proposes that the low- rate convergence of the Philippine- Eurasian plate against the background of passive subduction formed a high- angle subduction, which led to the formation of the western arc. After that, the northwestward accelerated motion of the Philippine Plate resulted in the reduction of the subduction angle, thereby the activity of the western arc stopped and the eastern arc began to form. The new proposed model does not need the subducted low- density materials to provide additional buoyancy to reduce the subduction angle. The two arcs are separated in the south by 50 km. We suggest that the potential reasons are that the oceanic crust age increases northward and (or) the Philippine plate rotates about Taiwan. Follow up work is needed to further confirm, falsify or quantitatively investigate their contributions. In this study, a evolution mechanism of Taiwan- Luzon double volcanic chain is proposed, which may be helpful to facilitate the understanding of the double volcanic chain and the subduction system, and can also provide an example for understanding other passive subduction processes.