Forced degradation tests of eldecalcitol API were conducted under acidic,alkaline,oxidative,light-exposed,and high-temperature conditions.Five degradation products were generated,namely(1R,2R,3R,5Z,7E)-2-(3-hydroxypropoxy)-9,10-secocholesta-5,7,10(19),24(25)-tetraene-1,3-diol(AD-1),(1R,2R,3R,5E,6Z,8Z)-2-(3-hydroxypropoxy)-9,10-secocholesta-5(10),6,8(9)-triene-1,3,25-triol(AD-2),(1R,2R,3R,5E,7E)-2-(3-hydroxypropoxy)-9,10-secocholesta-5,7,10(19)-triene-1,3,25-triol(AD-3),(1R,2R,3R,5E,6E,8Z)-2-(3-hydroxypropoxy)-9,10-secocholesta-5(10),6,8(9)-triene-1,3,25-triol(AD-4)and(1R,2R,3R,14S,5E,6Z,8Z)-2-(3-hydroxypropoxy)-9,10-secocholesta-5(10),6,8(9)-triene-1,3,25-triol(AD-5).Among them,AD-1 and AD-5 were not found in literatures.This study developed synthetic routes for AD-1 and AD-5,and optimized the synthesis process for AD-4.The structures of these products were confirmed by 1H NMR,13C NMR,and MS.This paper provides the references for the quality research of eldecalcitol,as well as its production,packaging,and storage.