Large complex technical programs/projects mainly involve the engineering systems to be developed and the organization systems in which the projects are carried out. It has been a common knowledge that systems engineering is an interdisciplinary approach to enable the realization of successful system. Some commonly used definitions of systems engineering are provided by the best known international technical standards, and they all have a common theme. Nowadays, great needs for systems engineering approach are emerging from major engineering projects in China, but there seems to be a confusion of "what systems engineering is" .The organization system is an open complex giant system. The holistic competence of an organization has an important impact on the success of projects. The systems perspective and approach are essential to organization management. The kernel issue is how to encourage people and how to cultivate an organizational creativity and productivity. In complexity study, this is the issue of the recognition of the micro-mechanism of system macro-emergency property. Neither analytical methods nor statistical methods are able to describe social system complexity quantitatively and accurately.