This paper points out that the natural factors(mainly is astronomical factors) and the greenhouse effect of climate warming are both important,and it is difficult to define which one is more important up to now.The results of climate warming are not bad things, but its advantage and disadvantage both can not be underestimated.The troop occurring periods in history mainly occurred in the warm period but not in the cold period.The future countermeasures can not pay attention to only one probability.