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/Wnet) and heat recovery efficiency (Ф). 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°C and R141b is the optimal working fluid when the temperature higher than 180°C. When the exhaust temperature ranges from 100°C to 220°C, the optimal pinch point at evaporator is about 15°C. Economic characteristic of system decreases rapidly with heat source temperature decrease. When the heat source temperature is lower than 100°C, ORC technology is uneconomical. ► The optimal working fluid is selected for different heat source temperature. ► The boiling temperature of working fluids can greatly affect the optimal evaporating pressure. ► The optimal pinch point at evaporator is about 15  C ► The ORC technology is unsuitable for the waste heat that the temperature is lower than 100 C.