A highly transparent Eu3 -doped CaGdAlO4 (CGA) single crystal is grown by the floating zone method. The segregation coefficient, x ray diffraction, and x ray rocking curve are detected, and the results reveal that the single crystal is of high quality. The f–f transitions of Eu3 in the host lattice are discussed. The D05–F72 emission transition at 621 nm (red light) is dominant over the D05–F71 emission transitions at 591 and 599 nm (orange light), agreeing well with the random crystal environment of Eu3 ions in a CGA crystal. The decay time of Eu:D05 is measured to be 1.02 ms. All the results show that the Eu:CGA crystal has good optical characterization and promises to be an excellent red- fluorescence material.