Surface water and groundwater are important constitutes of water resource system. Since the water transports and deposited in different ways within the medium between surface and ground, so the modeling and appraising method adopted are different. In the first time of water resources appraising of China, only the difference in national groundwater resources’ gross is up to 10000 billion tons (or about 1/8 of all the national groundwater resources). This data is twice of the data of the water transported from south to north or more. The author thinks that the main reasons for the total error of groundwater resource appraisal are: 1) In the nature, groundwater and surface water frequently converse and replenish with each other. It is improper to appraise them seperately. But in water resources appraising of China, from one level to three level sub areas, ground water moduli were not divided along with surface water together. 2) In water resources appraising, the computing methods of replenishment and evaporation for surface water and ground water are not be united, and the resource quantities’ iteration principles are different, leading to the inconformity of various results. 3) Basic data for water resource’s evaluation of China come from the different management department respectively. Water conservancy department manages surface water and agricultural water. On the other hand, constructed department manages the water for city use. For a few years, the groundwater had been managed by geologic and mining section, which, meantime, could pursue a part of monitoring work. They all have accumulated but different data of many years. The data of above three sections are the foundation on which the water resource’s evaluations in China proceed. The author thinks that in the first time of water resources evaluation of China, surface water should be evaluated according to river valley, while ground water be evaluated through hydrology geology unit, so that the gross’ error can be avoided in water resources’ appraising. The author also brings up the project of three level evaluation and sub area. In the groundwater resources’ quantity evaluation, one and two level sub area methods according to river valley are adopted. Three level sub area methods according to groundwater unites are used to resolve the problem of the water resources’ evaluation error.