The cloud is a natural phenomenon.It widely， frequently， irregularly appears in the earth sky and thus in the satellite imagery.The cloud in the remote sensing images largely reduces remote sensing image quality and usage ratio.The presence of clouds in satellite images is a significant obstacle to land surface studies.Clouds in satellite images must be precisely identified prior to any further analysis in any case.Cloud detection is a necessary step in the image data analysis processing.Therefore accurately extracting the location of the cloud area becomes a very meaningful research subject.This paper has proposed a cloud detection algorithm for MODIS image based on HSV color space.The HSV color space is first introduced in cloud detection study.Based on the different objects spectrum， MODIS instrument channel characteristic and the HSV positive transformable formula， the algorithm firstly has processed the HSV positive transformation for the pseudo-color image composed of the band 1， band 6 and band 26.Then to carry a threshold for the hue， we can get the final cloud detected results.The algorithm is simple， impersonal and fast.The results show that the algorithm is applicable to all the different scenes and seasons and has basically completed.