To　obtain　high-purity　MgB2　bulks,　using　magnesium　powder　and　boron　powder　as　starting　materials,　MgB2　bulks　were　successfully　prepared　by　conventional　pressureless　sintering　(PLS)　method　in　the　flowing　argon　atmosphere　at　the　ambient　pressure.　We　have　systematically　studied　the　process　of　synthesis　of　MgB2　and　focused　on　discussing　the　effects　of　various　parameters　on　impurity　of　the　sample　in　the　reaction　including　the　sintering　temperature,　the　sintering　time　and　the　ratio　of　starting　materials　and　have　obtained　the　optimal　conditions.　The　experimental　results　show　that　MgB2　bulks　with　single　component　were　fabricated　at　750°C　for　3　hours　when　the　ratio　of　Mg　and　B　is　1:2　&le　n　(Mg):n(B)　&le　1.2:2,　and　its　Tc　is　near　39　K.