To further improve the cycle efficiency with the heat transfer curves between higher than 350 degrees C heat resource and the evaporating working medium of the Kalina cycle and to reduce the exhaust temperature of heat resource, the dual-pressure vaporization Kalina cycle for cascade utilization of high-to-mid grade heat resource is proposed. The optimization was conducted for parameters in this modified Kalina cycle such as concentrations of work solution and basic solution, evaporation dew point temperature. Under the conditions of inlet temperatures of heat resource and cooling water of respectively 400 degrees C and 25 degrees C and the constraints of proper heat transfer pinch point temperature differences, the maximum evaporation pressure not exceeds 20 MPa, the vapour quality at the turbine outlet is greater than 0.85 and the exhaust temperature of heat resource is not lower than 90 degrees C, the optimum parameters are obtained that the work and basic concentrations are 0.45 and 0.272 respectively, the dew point temperature of evaporation is 300 degrees C, and the corresponding power recovery efficiency of the dual-pressure vaporization Kalina cycle reaches 27%, which is 17% higher than that of the Kalina cycle with optimum parameters. (C) 2015 Elsevier Ltd. All rights reserved.