Most of the public sectors in the world and in developed countries specifically acknowledge the importance of e-commerce to their countries and to survival of their businesses and in creating and encouraging an atmosphere for the wide adoption and success of e-commerce in the long term. The Investment for implementing e-commerce in the public sector is one of the areas which is focused in Government‘s action plan for cross- disciplinary IT development and e-readiness in government administration and the migration of e-commerce tools and practices into public sector organizations is changing the way of governments’ interactions and increasingly move to delivering information and services electronically which leads them in the use of technology to enable the delivery of government services. Public sector in Iran is already some way behind in this development while at the same time we know that it is relatively far advanced in terms of IT investment through e-readiness and they have limited power in explaining how and what level of e-readiness affects individual businesses' decisions to undertake e-commerce and the success of such efforts. So this study aims to explore the importance of an existing e-readiness approach for e-commerce success in public sector enterprises in Iran. This research hypothesized two main categories (organizational and external ) factors with eight sub factors which affect on e-commerce success which was included of five factors (success of development, cost saving, communications improvement, marketplace performance, overall satisfaction ) in KWPA (Khuzestan water & power authority ) as a case study in Iran. The research results mention that among the organizational and external parameters, the external parameters in a public sector which was observed as governmental readiness has the most affection on ecommerce benefits but the organizational readiness through success of development parameter affects on ecommerce benefits as well.