CaCu3Ti4O12　(CCTO)　ceramics　as　a　dielectric　material　are　of　potential　applications　in　capacitors　and　memory　devices,　however,　how　to　further　improve　the　dielectric　properties　of　CCTO　ceramics　is　still　a　challenge.　The　dielectric　behavior　of　this　material　can　be　manipulated　via　the　modification　in　composition,　and　Si　as　a　glass　phase　should　have　an　impact　on　the　properties　of　CCTO　ceramics,　this　work　investigated　the　effects　of　Si-doping　on　CaCu3Ti4O12　with　the　aim　of　improving　dielectric　characteristics.　CaCu3Ti4O12　ceramics　of　various　Si-doping　concentrations　were　synthesized　by　solid　state　reaction　method　at　1050　degrees　C.　The　microstructure　and　the　dielectric　properties　of　Si-doped　and　undoped　CaCu3Ti4O12　were　studied.　It　is　found　that　the　added　silicon　can　be　incorporated　into　the　structure　of　CaCu3Ti4O12,　a　certain　amount　of　Si-doping　would　facilitate　the　grain　growth,　promote　the　precipitation　of　intergranular　phase,　and　improve　the　compactness　and　homogeneity　of　CaCu3Ti4O12　ceramics.　Si-doped　CaCu3Ti4O12　samples　show　significantly　higher　dielectric　constant,　accompanied　by　larger　dielectric　loss.　The　temperature　dependence　of　dielectric　permittivity　epsilon　＇＇　for　various　frequencies　shows　three　successive　sets　of　peaks　attributed　to　intrinsic　relaxation　polarization　processes,　suggesting　that　Si-doping　has　little　influence　on　the　relaxation　mechanism　of　CaCu3Ti4O12　ceramics.