According to the actual releasing heights of 750 g meteorological balloon used at the Yangjiang station, the release heights of the 2000 g used in the comparing test organized by the CMA Meteorological Observation Center, and the release heights used during the 8th WMO intercomparison of radiosonde systems in Yangjiang, Guangdong, the influences of rainy and highhumidity weather conditions on the release heights of domestic meteorological balloons are studied. The results show that the influence of weather conditions on the releasing heights of domestic meteorological balloon is significant in rainy days or high humidity conditions. The research suggests that the rainproof and moistureproof of domestic meteorological balloons is the key to the problem of the unstable release heights for domestic meteorological balloons in some extent.