The rapid thermal annealing method is used to crystallize a glass/A1/BiGaDylG double-layer film (where BiGaDylG denotes dysprosium iron garnet films doped with Bi and Ga); the effective Faraday angle of the double-layer film is about 0.25° greater than that for glass/BiGaDyIG film and about 0.15° greater than that for common glass/BiGaDyIG/A1 double films in a wide thickness range; meanwhile the Curie point is decreased because of the aluminium atoms diffusing into the garnet film and substituting at octahedral and tetrahedral Fe3+ sites. The Curie temperature can be adjusted between 161 and 140℃ by means of delay annealing duration. The grain diameter and Faraday angle as functions of heating rate c and number of rapid recurrent annealings N have been presented, and are used to explain the mechanism of effective Faraday angle increase and grain size decrease, suggesting that glass/A1/BiGaDyIG films are promising candidates for blue light magneto-optical recording disks.