Unstandardized and standardized principal component analysis is applied to a series of 48 monthly Global Vegetation Index (GVI) data for the years 1986-1989 when NOAA-9 was transferred to NOAA-11. The first component is found to represent a sum of NDVI values. The second and third components show an annual NDVI cycle while the fourth and fifth component relate to a semi-annual cycle. The sixth component relates to the effect by the change of the NOAA satellite. That is, components except the sixth one are independent of the effect by the change of the satellites. In the 2nd to 5th principal components which relate to seasonal changes, there is no evident difference between unstandardized principal component and standardized principal component. However there are some differences between unstandardized principal component and standardized principal component in the 1st and 6th principal components.