Chip temperature becomes a critical design issue with technology scaling to nanometer-scale, especially for NoC systems with large number of cores and shrunken core size. To reduce peak temperature and balance spatial temperature distribution on NoC-based multi-cores chips, this paper proposes a temperature-aware task scheduling approach. The thermal profiles of tasks are first extracted by accurate temperature model. Then run-time task mapping heuristic is proposed considering transient core temperatures, thermal dissipation from adjacent cores, communication overheads and the thermal influence of physical position on chip. Voltage-frequency is also scaled down when timing constraint is met to reduce power consumption and core temperature. Experimental results show that the significant reduction of peak temperature and the temperature variance compared with the current approaches is achieved.