In the field of vision-based autonomous landing of unmanned aerial vehicle（UAV）

it is important to obtain the position parameters related to runway by computer vision.After gaining the equations of two edges of runway in the image pixel coordinate by image processing

the method to obtain angle between edge of runway and body of UAV is illustrated when the pitch of UAV is received.A method to obtain extrinsic rotation parameters of camera based on N vector is introduced.Compared with traditional method

this method reduces the number of nonlinear equations and raises the speed.Simulation experiment demonstrates this algorithm is simple and the result is precise and fulfils requests of UAV’s navigation system.