In this paper, the seasonal and non-seasonal features of the total cloud amount over Northern Hemisphere are analysed based on the data from 1966 to 1989. It is shown that the Northern Hemisphere has got two areas with bigger cloud amount, which are situated in the North Pacific and North Atlantic respectively, and also got one area with smaller cloud amout in the Northern Africa., The annual mean cloudness appears east-west oscillation. The areas with the bigger cloudness are just the areas with slighter interannual variability. And the position of the cloud areas vary obviously seasonally from winter to summer.The cloud amount in the high latitudes gradually increases from one month to another in the summer half year and decreases in the winter half year.The northerly and southerly moving of the areas with smaller cloud amount in the mid-lower latitudes is closely related to the northerly and southerly moving of the ridge at 500hPa subtropical high.