The mechanical properties of the nodular cast iron treated by troostite heat treatment were investigated, which technologies are control-cooling, adjustment at medium temperature and isothermal transformation. The fracture morphology and the microstructure were observed by scanning electronic microscope. The experimental results show that, the microstructure and mechanical properties in surface of the pieces were nearly same as that in the core after processing. Remarkable sudden change spot was not observed. The microstructure and performance with good uniformity and continuity have high stability.