Abstract: Using the data of daily air temperature and water-vapor pressure from 1978 to 2000 over the southeast Beijing, the spatial structure functions of the two elements are regressed for different seasons. Furthermore, based on the structure functions, the relationships between the error of linear and plane interpolation and distance are established. Finally, according to the principle that the standard error of interpolation should not exceed the standard error of observation, the maximum admissible spacing between stations of second group meteorological networks are estimated over the area.It is found that the equilateral triangle distributing is the best scheme to use, and the distance between stations should be less than 16 km. Firstly, the regressed spatial structure functions to the distances of the air temperature and water-vapor pressure are linear or close to linear. Over the southeast Beijing, the spatial structure functions increase monotonously with the distances, and have different values in different seasons. The season sequences in which the spatial structure functions of air temperature varies from largest to least are winter, autumn, spring and summer, and they are just opposite for the structure functions of water-vapor pressure. It illustrates that the temperature gradient is largest in winter, least in summer, and larger in autumn than in spring over the southeast Beijing, and the water-vapor pressure gradient varies from the largest to the least sequentially in summer, spring, autumn and winter, just oppositely to the condition of temperature gradient. The standard error of interpolation, maximum admissible error, and maximum admissible spacing all vary with seasons and distributing schemes, and the season sequences according to the standard error values is the same with that for the structure functions. When the standard error of interpolation is less than the standard error of observation, in all seasons, the equilateral triangle distributing has the least interpolation error, the largest maximum admissible error and admissible spacing between stations for the both elements. So the equilateral triangle distributing is the best scheme to use. With this distributing scheme, the distance between stations should be less than 16 km for temperature and 88 km for water-vapor pressure. So in a word, based on these two elements, the equilateral triangle distributing is the best scheme to use, and the distance between stations should be less than 16 km for the second group meteorological networks over the southeast Beijing.Further investigation shows that if consider the northwest high altitude region together with the southeast low lying region of Beijing, the equilateral triangle distributing is still the best scheme, but the distance between stations should be less than 4 km for the second group meteorological networks over the whole Beijing region. This is not consistent with the request of the second group meteorological networks. So the second group meteorological networks over the southeast and northwest region of Beijing should be designed separately, or some resource would be wasted.