Visually displaying the thickness change of the insulation layer of a solid rocket engine plays an important role in maintaining the working performance of the engine.Aiming at the problem of mutual restriction of small thickness changes in large-size structural workpieces, a three-dimensional visualization method of insulation layer thickness based on color rendering is proposed.Firstly, the curvature reduction method is used to preprocess the original point cloud data, and the characteristic information of the thickness change of the insulation layer is retained while the point cloud data is reduced in a large scale; The scan line triangulation algorithm based on optimization criteria is used to triangulate the simplified point cloud data. Then, based on the set datum, a color mapping model is constructed, the insulation thickness value is converted into color information, and it is rendered to show the thickness change of the insulation layer through color change.Experimental results show that while showing the insulation layer of an engine with a length of 11150mm, this method can accurately and intuitively display the thickness change of the insulation layer of less than 0.5mm.