In order to effectively utilize low grade energy at different temperatures, this paper presents three systems using liquefied nature gas (LNG) as cold source. 16 potential applicable organic working fluids are selected for different cycles and systems. In the meantime, thermodynamic and thermal-economic analysis and comparison based on a multi-objective optimal model has been done. The results indicate that, when the temperature of low grade energy is below 370 K, the single-system has the best performance, and the tripartite-system has the best performance when the temperature is above 370 K. Propane emerges as the most suitable working fluid for single-system and R245fa for tripartite-system. Meanwhile, best work conditions have been calculated for single-system and tripartite-system. Moreover, the turbine's cost is the largest for both systems because of the large expansion ratio. (C) 2017 Elsevier Ltd. All rights reserved.