Existing P2P systems are mostly confined to the domain of file sharing systems, which in many aspects differ from decentralized E-Commerce, e.g., peer behavior mode and capability diversity. Therefore, we researched on the distinct properties of decentralized E-Commerce, especially for B2B level E-Commerce, and accordingly, propose a decentralized E-Commerce oriented service discovery system, named SOUNDE. The system can be viewed as a two-layer architecture, with the upper layer composed of many E-Commerce Domains forming a DHT-based topology, then each Domain composed of all the related peers in that specific Commerce Domain, including Service Requesters and Service Providers of it, forming an unstructured topology which applies SophiNode service discovery algorithms. Meanwhile, we also put forward GovNode, which plays the role of joint between the two layers. Gathering all the peers within same Commerce Industry into a logic subnet (Commerce Domain), then all Domains into DHT structure, the fundamental purpose of SOUNDE is to diminish the searching scope of each service query, (i.e. Reduce the network load), and allow the system to scale. At the end, we present our simulation and analyze the results.