In　this　paper,　we　characterize　a　mixed　graph　(Formula　presented.)　which　contains　(Formula　presented.)　edge　and　arc-disjoint　spanning　mixed　arborescences　(Formula　presented.),　such　that　for　each　(Formula　presented.),　the　cardinality　of　(Formula　presented.)　lies　in　some　prescribed　interval.　This　generalizes　both　Nash-Williams　and　Tutte＇s　theorem on　spanning　tree　packing　for　undirected　graphs　and　the　previous　characterization　on　digraphs　which　was　given　by　Cai and　Frank.　©　2021　Wiley　Periodicals　LLC