Aimingtotheestimationofsourcenumbers,mixingmatrixandseparationofmixingsignalsunderunderdeterminedcase,thearticleputsforwardamethodofunderdeterminedblindsourceseparation(UBSS)withanapplicationinultra-wideband(UWB)communicationsignals.ThemethodisbasedonthesparsecharacteristicofUWBcommunicationsignalsinthetimedomain.Firstly,findingthesinglesourceareabycalculatingtheratioofobservedsamplingpoints.Thenanalgorithmcalledhough-windowedmethodwasintroducedtoestimatethenumberofsourcesandmixingmatrix.Finallytheseparationofmixingsignalsusingamethodbasedonamendedsubspaceprojection.ThesimulationresultsindicatethattheproposedmethodcanseparateUWBcommunicationsignalssuccessfully,estimatethemixingmatrixwithhigheraccuracyandseparatethemixingsignalswithhighergaincomparedwithotherconventionalalgorithms.Atthesametime,themethodreflectsthehigherstabilityandthebetternoiseimmunity.