The　transparent　Co2+:ZnAl2O4-SiO2　block　glass　ceramics　with　doping　of　transition　metal　ions　Co2+　were　synthesized　by　sol-gel　method.　The　DSC-TG,　X-ray　diffraction,　Fourier　infrared　spectrometer　and　visible　and　near-infrared　absorption　spectra　were　performed　to　study　the　microstructure　and　the　optical　properties　of　glass　ceramics.　The　results　show　that　the　average　size　of　the　ZnAl2O4　nanocrystals　is　12-14　nm.　The　glass　ceramics　exhibit　a　broad　absorption　band　in　the　range　of　1200-1600　nm.　And　the　absorption　coefficient　enhances　with　the　increase　of　heat-treating　temperature,　which　is　characteristic　of　4A2→4T1(4F)　transition　from　the　tetrahedral　Co2+　ions.　The　absorption　cross　section　reaches　1.15×10-19　cm2　when　the　heat-treating　temperature　is　up　to　1000　,　which　means　that　it　can　be　applied　in　the　passive　Q-switch　turnable　laser.　©,　2014,　Science　Press.　All　right　reserved.