Nanostructured ZrO2 was prepared successfully by mechanically activated solid state reaction. The structural and microstructural of products were monitored using X-ray powder diffraction (XRD), transmission electron microscopy (TEM). The effects of ball milling speed and calcined temperature on products were monitored by XRD. The results of XRD show that the most suitable ball milling speed is 150r/min, and the calcined temperature is 600°C. TEM images show that ZrO2 particles prepare at heating rate of 5°C/min have several advantages in the morphology, spherical shape, narrow size distribution with no hard aggregation, and the particle size is about 15 nm, and at the heating rate of 2.5°C/min, a network structure ZrO2 can be prepared for the first time.