A method of expressing in vivo heart-specific fluorescence in transgenic line of zebrafish is developed, which provides a research model for studying heart-related gene functions and performing gene therapies in the future. The method comprises the following steps. Firstly, a plasmid is constructed. This plasmid construct includes the upstream regulatory region, the exon 1, the intron 1, and the exon 2 of cmlc2 gene, cDNA of GFP, wherein the cmlc2 gene and GFP cDNA form a cassette, and inverted terminal repeats from adeno-associated virus are flanked at both sides of this cassette. The plasmid construct is linearized and microinjected into one-celled zebrafish fertilized eggs. Lastly, the heart-specific fluorescent expressed zebrafish are selected and the germline-transmitting transgenic strain is generated.