Wooden artifacts from Gansu represent the highest level of Han Dynasty carving skills in China. Being rotten is a typical feature of these wooden artifacts—usually the degree of cellulose degradation is up to 50%. The inherent properties and defects of the material and the sensitivity to the humidity and moisture in the environment easily cause the effects of “wet expansion and dry contraction”, which is harmful to the preservation and conservation in the later stage. In view of the disadvantages and issues in the current safety assessment technology, we conducted profound analyses of the methods, wood material characteristics and properties, and combed through relevant physical parameters used to measure and characterize material shapes and structure changes. We also applied modern analytical instruments and mature analysis technologies to observe morphology and analyze testing data of collected samples. The study result show that 1) the moisture content of the wooden core, as the determining factor affecting the structure and shape stability of rotten wood ware, was the only indicator of the safety assessment; 2) the volumetric weight, degree of fiber crystallization and of fiber degradation of the wooden core, as the characterization parameters considering material physical and chemical properties, objectively reflecting the actual changes of the material, could be used as a reference index for the quantitative assessment; 3) the safety change range of the moisture content of the wooden core was 9.3%~14.3%, with a safety fluctuation range of ± 5%. According to the above results, we made relevant definition standards for the safety assessment of rotten wooden artifacts:1) when the wood moisture content fluctuates and changes in the safe range, the characterization parameters change slightly, and the object is basically safe; 2) when the wood moisture content fluctuates frequently beyond the safe range, serious changes in the morphology and structure of the rotten wood often occurs, with the volumetric weight and fiber crystallization degree decreasing, and the fiber degradation degree increasing; 3) when the object loses the basic ability to maintain its balance effect—when the characterization parameters are extremely abnormal, especially when the lignin content reaches 85% and the cellulose is almost completely degraded—it is endangered. Finally, combining and combing through the analysis results, we designed and created a scientific and standardized framework of the safety assessment technology for rotten wooden artifacts. The technology not only adopts the combination of quantitative and qualitative ways, with the characterization of being data and evidence-oriented, but is also simple and practical.