The paper presented a working fluid selection and parametric optimization using a multi-objective optimization model by simulated annealing algorithm. The screening criteria considered included heat exchanger area per unit power output (A/W-net) and heat recovery efficiency (Phi). The independent parameters are the evaporation and condensation pressures, working fluid and cooling water velocities in tubes. A comparison of optimized results for 13 working fluids shows that boiling temperature of working fluids will greatly affect the optimal evaporating pressure. R123 is the best choice for the temperature range of 100-180 degrees C and R141b is the optimal working fluid when the temperature higher than 180 degrees C. When the exhaust temperature ranges from 100 degrees C to 220 degrees C, the optimal pinch point at evaporator is about 15 degrees C. Economic characteristic of system decreases rapidly with heat source temperature decrease. When the heat source temperature is lower than 100 degrees C, ORC technology is uneconomical. (C) 2012 Elsevier Ltd. All rights reserved.