The operation characteristic and performance comparison of low-grade organic Rankine cycle (ORC) using R245fa, R123 and their mixtures have been investigated. The heat source temperature is set to be 120 degrees C, while the mass flow rate is controlled by adjusting the pump frequency. The basic operation parameters are first examined, while the detailed operation characteristics of pure and mixture working fluids are addressed. The system overall performance, including thermal efficiency and system generating efficiency, for pure and mixture working fluids are explored. The experimental results show that the mixtures own a relatively higher pump power consumption and enhancing the pump performance is also significant for ORC application. Whether the mixtures exhibit better thermodynamic performance than the pure working fluids depend on the operation parameters and mass fraction of mixtures. 0.67R245fa/0.33R123 owns the highest maximum net electricity output of 1.67 kW, 4.38% higher than that of R245fa and 63.73% higher than that of R123. Compared to the pure working fluids, the mixture working fluids own a better thermodynamic performance and a moderate economic performance. (C) 2017 Elsevier Ltd. All rights reserved.