Vinh Chau district of Soc Trang province is the largest "purple onion" region of the country. However, production and distribution of purple onion are unstable in recent years, onion product has not met the market needs in terms of quality and quantity, high competition, lack of planning, instability of export market, lack of horizontal and vertical linkages for large scale production and distribution. Value chain analysis of purple onion applies the value chain approach of Kaplinsky & Moms (2001), the ValueLinks method of GTZ (2007) and Marking value chains work better for the poor (M4P, 2(08). Research results show that purple onion production in Vinh Chau has high competitive and comparative advantages. Value chain of purple onion has four actors and four market channels including two channels for domestic users and two channels for export. Total gross profit of purple onion in export channels is higher ,than those of domestic distribution, less agents in a chain market channel, higher benefits to producers. Furthermore, researchers also propose four strategic solutions for upgrading value chain of purple onion in Vinh Chau in the coming time.