Abstract: In September,1980,an experiment on application of singlelens multispectral photography wa carried out successfuly on the grassy marshland at Jinyuetan area in Changehun and the marshland at Huangnihe in Dunhua County in Jilin Province. The writer used the self-designed and-fabricated low-altitude tethered balloon as a platform of remote sensing for multispectral photography. The height taken for multispectral photography was from 10 to 100 meters. Because of the aerial influence and the limitation imposed by the ground resolution, the photographs taken by satellite and aircraft can be applied only to provide partial material for marsh researching. But the low-altitude tethered balloon multispectral photographs Can supply some additional new information. This information is of benefit to the quantitative analysis for the Classification and distribution of the marsh vegetation, the type of the marsh and its boundaries, etc. (1) By detecting and Comparing spectral densities in four Channels (400nm—800nm), three different kinds of marsh vegetation can be distinguished. Typha Orientalis Can be recognized more easily in IR Channel than in the other Channels. (2) The old buggy routes in the marshland Can bedetermined by colour compositional images.The application of these images Can also make correct sketch of the marsh classification and Calculate the area of the dispersed marsh vegetation. (3) It is a new means of applying digitized image processing to take quantitative measurement of the Colour Compositional image. According to the, colour-minus △E. it has been proved that the IR-G-R image is better than the IR-R-G image in recognizing various marsh vegetation. As a result of this experiment, the low-altitude tethered balloon is proved to be an economic and effective platform for multispectral photoghaphy. It is an easy and Convenient method to collect data of remote sensing. But it has a shortcoming that the tethered balloon moves along with the wind.So the writer suggests to develop a motor-balloon.