Abstract: The paleoclimate effects of six asteroid impact events on the Earth happened in Cenozoic are studied by employing a energy-balance model. The result shows that when the dusts produced by these impacts entered the stratosphere, the average temperature of the Earth decrease to below 0℃, the disturbances caused by the impacts on temperature are last for about 30 years in maximum. It is first time that greenhouse effect of the carbon diozide produced by global fire and decomposition the died animals and plants is considered in modeling. However, at maximum, carbon dioxide produced by these two effects (global fire and decomposition of the died animals and plains) only makes an increase of 67% the atmospheric carbon dioxide, the greenhouse effect is so small that it can be negleted while compared with the effect of the antigreenhouse effect of the dusts. When the global carbon cycle is considered,these two effects on atmospheric carbon dioxide are last for 100 years.