A new method is developed to estimate fundamental matrix (F matrix). We first find two parameters in the 8-parameter F model by the new constraint developed in this paper, the two parameters are the affine coordinates of an epipole. Then we obtain the rest 6 parameters by solving a set of linear equations. Finally, our method is tested with many real images and compared with the 8-point method and some iterative algorithms, the results show that our method has many advantages, such as the obvious geometrical meaning, the fewer matching pairs needed for calculation and high accuracy F matrice.