在ISO9000过程“输入-输出”模型下，过程质量概念很难得到正确的阐释。从过程的“白箱”理论出发，以铁路建设工程的基本作业单元6M1E为例，给出了过程质量概念的科学涵义及过程质量模型。指出基本作业单元系统的过程包括工艺自然过程、作业过程、管理过程；基本作业单元系统的过程质量取决于3个子过程之间的相互联系和相互作用，同时还受到外界扰动输入因素的影响。最后以现浇预应力砼连续箱梁施工过程为例，阐述了该理论在铁路建设工程质量管理中的具体应用。

In the ISO9000“input- output”process model，the concept of process quality is difficult to get the correct interpretation. From the point of view of the process's“white box” theory，this paper puts forward the scientific meaning of the concept of process quality and the process quality model by taking the basic operating unit of6M1E in the railway construction project for example. The basic operating unit system consists of the technological natural process，operation process and management process；the process quality of the basic operating unit system depends on the interrelation and interaction among those three sub- processes，and also subject to the impact of the external disturbance input factors. Finally，the cast- in- situ prestressed concrete continuous box girder construction process is utilized to elaborate the specific application of this theory in the quality management of the railway construction project.