The invention discloses an estimating method for normal vectors of points of three-dimensional point clouds. The estimating method comprises the following steps: determining a k nearest neighbor point of each point in a space neighbor field; calculating an initial normal vector of each point according to the k nearest neighbor point; fitting a plane; choosing the k nearest neighbor point with 60%-80% of a nearest distance according to a distance from the k nearest neighbor point to the plane; rechoosing the k nearest neighbor point forming 60%-80% of a smallest included angle with the normal vector of the k nearest neighbor point chosen for the first time; eliminating noise points; calculating the stable normal vectors of the chosen points; and traversing the point clouds so as to obtain the stable normal vectors of each point. The estimating method successively uses the distance and the direction consistency to judge and eliminate unstable points in a K nearest neighbor, so that the more stable normal vectors of the points in the point clouds can be obtained by calculating, the more stable calculating parameters can be provided for the registration, clustering, division and the like of the point clouds, and the inhibiting ability for noises can be improved.