The invention relates to a method for monitoring vegetation water source conservation amount change. The method comprises the steps of acquiring global land total water reserve change data, rainfall,actual evapotranspiration, soil water reserve, snow melting amount, snow water reserve, surface water reserve, underground water reserve, water resource amount change amount, dry branch and fallen leaf layer interception amount, average natural water content, maximum water holdup and litter accumulation amount; preprocessing data, and calculating the vegetation canopy water storage variation; calculating interception variation of a dry branch and fallen leaf layer; calculating soil water storage variation; and determining the water conservation variable quantity according to the vegetation canopy water storage variable quantity, the dry branch and fallen leaf layer interception variable quantity and the soil water storage variable quantity. A traditional method for calculating the soil water storage capacity through the product of the soil layer thickness and the non-capillary porosity is abandoned, the soil water content remote sensing data provided by NASA is used for calculating thesoil water storage variable quantity, and new technical support and reference are provided for ecological restoration process, ecological effect evaluation and water conservation evaluation.