Gambling in Macao has been legal since 1847，and has experienced very rapid growth after gaming liberalization in 2002. During the period，the market structure of the gaming industry was from perfect competition to complete monopoly to oligopoly. As the leading industry and pillar industry of Macao，the market structure of the gaming industry is crucial to the development of the industry itself and the overall economic development of Macao. Using the SCP model in modern industrial organization theory，this paper analyzes the market structure，conduct and performance of Macao’s gaming industry since the liberalizing of casino license. It is found that the market structure of the gaming industry in Macao is in the boundary between competition and monopoly，and the gaming companies use more non-price competition strategy. As an oligopoly market，the economic performance of the gaming industry is better than that of the complete monopoly market. Further，between the development of the gaming industry and the moderate and diversified development of the economy，there has been a trend of change in the industrial structure. The optimization of the market structure of the future gaming industry will boost the moderate and diversified development of the Macao economy.