A method of measuring 3D attitude of objects based on inclined angle of the lines between feature points is proposed,which is applicable to the condition that inter parameter is unknown and object is in a long distance.Synthetic images are applied to verify the correctness of the proposed method.As a result,the mean of absolute value of attitude error is less than 0.6°,and when the size of target are 350 pixels,the measuring error is less than 0.5°.The result shows that the proposed method is with highly correct and strongly convergent.