The　influence　of　C6H16N2　addition　on　the　microstructural　and　superconducting　properties　of　MgB2　was　systematically　investigated.　Unlike　previously　reported　carbon　sources,　the　C6H16N2　additive　had　no　effect　on　the　lattice　parameters　of　MgB2.　However,　the　obvious　improvement　of　critical　current　density　(J(c))　was　obtained　for　C6H16N2　added　MgB2　without　carbon　substitution　for　boron.　The　average　grain　size　was　reduced　with　the　addition　of　C6H16N2.　Additionally,　different　numbers　of　spherical　MgB2　grains　appeared　inside　the　C6H16N2　added　MgB2.　As　the　added　amount　of　C6H16N2　increased,　the　active　cross-sectional　area　fraction　(A(F))　values　first　increased　then　decreased.　The　possible　reasons　for　these　results　have　been　discussed.　The　additive　C6H16N2　resulted　in　a　small　depression　in　T-c　and　slightly　increased　the　Delta　T-c　of　MgB2　at　0　T.　The　H-c2　(T)　and　H-irr　(T)　values　of　C6H16N2　added　MgB2　samples　are　larger　than　those　of　pure　MgB2　at　temperatures　below　25　K.　It　was　concluded　that　the　reduced　grain　size　and　the　improved　grain　connectivity　were　mainly　correlated　with　the　enhancement　of　the　J(c),　F-p,　H-c2,　and　H-irr　performances　in　C6H16N2　added　MgB2　superconductors.