Four kinds of new alkylenediaminoalkyl-bis-phosphonic acid derivatives with alkylenediaminoalkyl functional groups in the molecule were synthesized and their smoke density(Ds) were tested. These alkylenediaminoalkyl-bis-phosphonic acid derivatives were prepared in yields(76-97.3%) by one step reaction of the phosphorus acid with amine and aldehyde. Smoke density was measured by the method of ASTM E 662. The values of smoke density were obtained from 234.7 to 437.9. The smoke density of compounds with two phosphonic acid structures were increased more than that of compounds with one phosphonic acid structure. In addition, there was correlation between the smoke density and the number of nitrogen atoms in amino group attached to mono- or di-phosphonic acids group.