The invention relates to a preparation method of transparent tetravalent chromium-doped yttrium aluminum garnet ceramics. The preparation method comprises the following steps: weighing raw material powder according to a stoichiometric ratio of a to-be-prepared ceramic component structural formula (Al1-xCrx)5CayY3-yO12 (x is not smaller than 0.001 and not larger than 0.01, and y is not smaller than 10x and not larger than 40x); adding a sintering aid and a charge compensating agent; mixing by ball-milling to obtain a slurry material; drying and sieving the slurry material and then molding to obtain a biscuit; calcining to remove volatile impurities; sintering the biscuit in vacuum at the temperature of 1730 to 1850 DEG C for 4 to 30 hours; subsequently annealing in air at the temperature of 1300 to 1550 DEG C for 10 to 25 hours to obtain compact Cr<4+>:YAG transparent ceramics. The Cr<4+>:YAG transparent ceramics prepared by the method disclosed by the invention are high in compactness, good in uniformity, free of segregation, reasonable in grain graduation distribution, free of abnormal grain growth, free of grain interior and intergranular pores and high in penetration rate, and have the conditions for being a laser gain medium.