系统分析了薄壁件定义本质 .薄壁件在工程上的判断准则 ,并对其进行了理论研究 ,指出了传统薄壁件判断准则的局限性 .从理论上论证了瞬时薄壁件的存在性 ,计算出物体成为薄壁件的瞬时时间并论证了瞬时物体成为薄壁件的条件 .这有利于薄壁件判断准则的科学正确性 ,扩展了薄壁件适用时间范围 ,弥补传热学中薄壁件判断理论的缺陷 This paper systematically analyzes the definition essence of thin-walled parts, the engineering judgment criterion of thin-walled parts, and makes a theoretical study on it, pointing out the limitations of the traditional thin-walled parts judgment criteria, and theoretically demonstrates the existence of instant thin-walled parts The instantaneous time when an object becomes a thin-walled member is calculated and the condition that an instantaneous object becomes a thin-walled member is calculated, which is in favor of the scientific correctness of the thin wall member judgment criterion, extends the applicable time range of the thin-walled member, Defects in judging theory of middle and thin wall parts