1. A searching method for plane of 3D model, using an editing software of 3D model, the method comprising: a) importing a first 3D model data and opening a first 3D model according to the first 3D model data; b) obtaining an outline of the first 3D model; c) obtaining coordinate information of a plurality of coordinate points within the outline; d) setting one of three axes of the first 3D model to be a datum axis; e) setting a lowest point of the outline of the first 3D model based on the datum axis to be a locate point; f) extending from the locate point along another two of three axes to search all of the coodinate points within the outline at a substantially similar height of the datum axis with the locate point; g) reserving the coordinate information of the coordinate points being continual and capable of constituting a plane area; h) after the step g), if the locate point is not a highest point of the outline on the datum axis, amending value on the datum axis to add a fixed variable of the locate point; and i) after the step h), executing the steps f) and h) according to the amended locate point.