Isothermal　compression　of　hydrogenated　Ti6Al4V　alloy　was　carried　out　on　a　Gleeble-1500D　simulation　tester　at　the　strain　rate　3　x　10(-3)　s(-1)　and　high　temperatures.　Before　the　isothermal　compression,　a　simplified　thermohydrogen　processing　(THP)　was　used　for　Ti6Al4V.　Attention　was　paid　to　the　effect　of　THP　on　subsequent　compression　behaviour.　The　results　show　that　hydrogen　can　effectively　lower　the　flow　stress　and　deformation　temperature　and　enhance　the　strain　rate　sensitivity　index　(m　value)　for　isothermal　compression.　The　increasing　amount　of　beta　phase　and　the　ultrafine　and　equiaxial　microstructure　precipitated　between　the　original　alpha　or　beta　laths　are　the　main　reasons　for　the　simplified　THP　to　improve　the　formability　of　Ti6Al4V.