As one of the important part of urban green lands, the riparian wetland park has good ecological environment and various landscape resources, and plays an irreplaceable role in adjusting the climate, beautifying the environment and maintaining regional ecological balance. So, study on the ecological effects of urban riparian wetland park not only have theoretical significance, but also have practical significance to improve living environment. In order to study the humidifying effect of different underlying surfaces from horizontal and vertical directions, the authors monitored the air humidity below the height of 1.5 m above the ground of various underlying surfaces, including a cement pavement (14 m wide), arbor-grass lands (58 m wide), and shrub lands (22 m wide), during 10-12^th October, 2012, 27-29^th September and 2^nd, 3^rd and 6^th October, 2013, when it was sunny day without wind (or the wind speed less than 0.2 m/s), in Taiping riparian wetland park of Shijiazhuang, Hebei Province. And compared the results with the monitoring data of bare land, which has the similar size to the monitoring area and free from plants and water. The research results could be summarized as follows: First, the humidifying effect of vegetation can strengthen with the increase of air temperature and the correlation coefficient surpasses 0.8. The humidifying effect is the strongest at 10:00-14:00 when the temperature is the highest on the midday. The humidifying effect is 4% more than that at 8:00, and 8% more than that at 18:00. Second, the humidifying effect is the strongest close to the ground surface, then it reduces toward up progressively from the height of 0.2 m, and the lapse rate is 1%-2%. Third, the humidifying effect of ground surface with different land covers from strong to weak are: shrub lands, arbor-grass lands, river and cement pavement, the shrub lands is 5%-7% more than that of arbor-grass lands. Four, the humidifying effect keeps a stable state in the same season where the structure and canopy density of the green lands have no obvious change. Last, the humidifying effect of green lands in autumn is weaker significantly than in summer, but the relationship between humidifying effect of green lands and air temperature has the same tendency in different seasons. In addition, the vertical variation of humidifying effect and the difference of various green lands with different structures also have the same tendency in different seasons. All of above present the general rules of humidifying effect of green lands. Thus it can be seen that the rational allocation on various types of green lands in wetland parks can improve the atmosphere environment more effectively.