The precept paper deals with the effect of salinity of saline soil on distribution and antagonistic properties of streptomyces. The results obtained are summarized as follows: 1. The number of actinomycetes is closely correlated with the salinity of saline soils in northern Jiangsu Province. It decreases with the increase of soil salinity while it is less than 0.2%. The curve of actinomycetes tends to be flat, when soil salinity is over 0.2%. 2.456 antagonistic actinomycetes out of 632 isolated from 6 saline soils with different salinity. The number of actinimycetes in cultivated land with low salinity is higher than that in virgin land with rather high salt content. However, the percentage of antagonists in total a,ctinomycetes in virgin saline soils is higher than that in cultivated land. 3. Numbers of the groups of streptomyces in cultivated soils are larger than that in virgin saline soils, and the kinds of group are different greatly between the two soil types. Aureus group is predominant in the desalinized soils cultivated for 20 years, while in virgin saline soils with high salinity Roseospours is predominant, and Cinereus comes to the neat. 4. Streptomyces with wide antimicrobial spectrum commonly occur in cultivated soils, among which Aureus and Griseofuscus are more effective in antagonism against both bacteria and pathogenic fungi. The antagonistic intensity of those groups range from 40-70%. In virgin saline soils, most of the isolates with antagonistic action belong to Roseosporus, Cinereus, Glaucus and Flavus groups and their antagonism are usually confined to Staphylococcus aureus, Bacillus subtilis or Monilia albicans.