Si-rich　Mo-Si-B　powders　(Mo-62Si-5B　at%)　were　deposited　on　Nb-Si　based　alloy　by　laser　cladding　assisted　with　ultrasonic　vibration.　The　obtained　coatings　mainly　consist　of　MoSi2　and　(Mo,　X)5Si3　(X　=　Nb　and　Ti).　With　the　introduction　of　ultrasonic　vibration　during　laser　cladding,　the　lath-shaped　MoSi2　phase　transforms　into　cellular　gradually.　Meanwhile,　the　discrepancy　on　the　microstructure　of　the　top　region　and　the　bottom　region　is　eliminated　gradually,　indicating　that　the　cavitation　and　acoustic　streaming　of　ultrasonic　vibration　not　only　refines　the　microstructure,　but　also　homogenizes　the　element　and　phase　distribution　in　the　coatings.　High-temperature　oxidation　experiment　at　1250　℃　were　conducted　to　assess　the　oxidation　resistance　of　the　coatings.　Compared　with　Nb-Si　alloy,　the　coated　specimens　have　much　lower　oxidation　weight　increase.　Furthermore,　with　the　assistance　of　ultrasonic　vibration,　the　oxidation　resistance　of　the　coating　is　enhanced　further.　The　oxide　scales　on　the　coatings　consist　of　two　layers:　an　upper　amorphous　aluminoborosilica　with　TiO2　particles　dispersed　and　a　lower　crystalline　SiO2　layer.　With　the　introduction　of　ultrasonic　vibration,　the　microstructure　of　the　coatings　is　refined,　resulting　in　more　phase　and　grain　boundaries　in　the　coatings.　Therefore,　the　diffusion　of　the　elements　to　the　surface　is　accelerated　and　the　protective　oxide　scale　can　be　formed　quickly.　©　2023　Elsevier　B.V.