The water quality deterioration is a major reason of contradiction between water supply and demand. Rational allocation of water quantity and quality to improve water utilization efficiency and water supply reliability is the inevitable requirement of healthily development of city. Based on the harmony theory and concept of dual water supply, Taking Xinmi urban area as a case study, the paper calculated the harmony degree of water allocation under different schemes and years. The research can provide the method of quantitative analysis for optimal allocation of water resources.