C-axis　oriented　Ga-doped　ZnO　(GZO)　films　with　various　thicknesses　were　deposited　on　glass　substrate　by　radio　frequency　(RF)　magnetron　sputtering.　The　dependence　of　crystal　structure,　electrical,　and　optical　properties　of　the　GZO　films　on　crystalline　size　were　systematically　studied.　The　results　showed　that　the　texture　coefficient　of　(002)　peak　(TC(002))　decreases　with　increasing　crystalline　size.　The　Hall　mobility　mu　was　reciprocal　to　electron　effective　mass　and　the　fitted　relaxation　time　tau　was　0.11　+/-　0.01　mu　s.　With　the　increase　of　average　crystalline　size,　the　resistivity　increased　slightly,　which　is　caused　by　the　competition　of　(002)　and　(101)　plane,　introducing　in　some　defects　and　leading　to　carrier　density　reduction.　The　optical　band　gap　was　in　the　range　from　3.454　to　3.319　eV　with　increasing　crystalline　size　from　26.96　to　30.88　nm,　showing　a　negative　relationship.　The　dependence　of　optical　band　gap　(E-g(op))　on　the　crystalline　size　(R)　can　be　qualitatively　explained　by　a　quantum　confinement　effect.　The　relationship　between　E-g(op)　and　R　of　GZO　films　suggests　that　tuning　up　optical　properties　for　desired　applications　can　be　achieved　by　controlling　the　crystalline　size.