Higher　manganese　silicides　(HMS)　bulk　materials　with　the　nominal　compositions　of　MnSix　(x　=　1.60,　1.65,　1.68,　1.73,　1.81,　1.85)　were　prepared　by　arc-melting,　annealing　and　spark　plasma　sintering.　The　phase　structures　and　morphologies　of　the　samples　were　investigated,　and　their　thermoelectric　properties　were　measured　from　300　degrees　C　to　600　degrees　C.　The　analyses　of　phase　compositions　revealed　that　the　intensity　of　X-ray　diffraction　peaks　was　firstly　enhanced　and　then　weakened　along　with　x　value　increasing.　The　phase　composition　were　of　HMS　and　MnSi　for　x＜1.73　samples,　and　were　of　the　HMS　and　Si　for　x　＞=　1.73　samples.　It　was　shown　that　the　thermoelectric　properties　of　the　samples　were　affected　strongly　by　the　metallic　MnSi　phase　and　the　semiconducting　Si　phase.　The　electrical　conductivity　decreased　continuously,　while　the　Seebeck　coefficients　increased　with　x　value　increasing.　In　addition,　the　thermal　conductivity　decreased　firstly　and　then　increased　with　x　value　increasing.　Furthermore,　it　was　showed　that　the　thermal　conductivity　remained　constant　at　lower　temperature　and　then　increased　sharply　because　of　the　contribution　of　electron　thermal　conductivity　at　temperature　higher　than　450　degrees　C.　The　MnSi1.68　sample　had　the　highest　dimensionless　figure　of　merit　ZT　0.36　at　400　degrees　C,　as　a　result　of　its　highest　electrical　performance　(power　factor)　and　moderately　low　thermal　conductivity.