Abstract: A generalized extension for the close condition of equations, which is satisfied with asymmetrical jet formation problem, is developed from head-on collision to asymmetrical oblique collision between two incoming streams. The geometrical theory of 2D planar asymmetric jet formation is presented. The critical condition and theoretical formula are obtained, which describe the formation of asymmetric jet. Variations of the width and direction of outgoing flows with collision anlge and initial configuration are theoretically predicted and numerically simulated under oblique collision. Theoretical results are in agreement with numerical results.