A method for searching plane area on a 3D model comprises following steps of: obtaining an outline of the 3D model; setting a lowest point of the outline based on a datum axis to be a locate point; extending from the locate point along another two axes to search all coordinate points within the outline at a substantially height on the datum axis with the locate point; reserving of the information of the continual coordinate points which can constitute a plane area; recording the plane area; amending value on the datum axis to add fixed variable of the locate point; executing above steps repeatedly until the locate point is amended to be the highest point of the outline based on datum axis. The present disclosure can actually search for all plane area on the outline of the 3D model, so as to help the combination with other 3D models.