Abstract: A method for computing the value of eave correction by using the single close range image of a building is introduced.In the method the digital lean image and the conditions of geometry and restriction of the framework appearance of building are used.According the cross ratio invariability and perspective reversion,the relation among the vanishing points,the spatial beelines and their projections in image is determined,and the width of the eave can be calculated.Experimental results show that it meets the requirements.