A method for optimizing reduction and content of total titratable alkali of green liquor of a recovery boiler. The method comprises producing green liquor in a dissolving tank by conveying smelt and weak white liquor into the dissolving tank and measuring at least the contents of sodium sulphate, sodium hydroxide, sodium sulphide, and sodium carbonate of the green liquor. The method comprises controlling at least a process parameter of a recovery boiler to maximize the reduction of the recovery boiler and controlling the flow of the weak white liquor into the dissolving tank to optimize the content of total titratable alkali of the green liquor. In addition, a system for producing green liquor with optimized reduction and content of total titratable alkali. The system comprises a first sensor arrangement, a first and a second regulator, and a processing unit arrangement configured to perform the method.