The sonic muscle of toadfish is the fastest vertebrate muscle ever measured, and the rate of transport of Ca2+ and dissociation of cross-bridge are also fatest. Parvalbumins are Ca2+-binding proteins present in vertebrate muscle, and they can aid muscle relaxation. Several isoforms of parvalbumin had been identified and presented in variable proportion in different kinds of muscles (e.g. red muscle, white muscle and pink muscle). Both male and female grunting toadfish (Allenbatrachus grunniens) have intrinsic sonic muscles attached on swim bladders. The morphology of male and female sonic muscle was compared, and no significant differences in both length, width, thickness and weight were found. SDS-PAGE and western blotting were used to determine the total parvalbumin expression and identify the parvalbumins from sonic muscle and body white muscle. There were no significant differences in total parvalbumin expression in sonic muscle and body white muscle. The result indicates that there is no positive correlation between high content of parvalbumins and speed of muscle relaxation. In native-PAGE, two and four parvalbumin isoforms were identified from sonic muscle and body white muscle, respectively. The estimated size of Parv1, Parv2 and Parv3 size in grunting toadfish¡¦s sonic muscle were 10kDa, 10.5kDa and 10.5kDa, respectively, and the isoelectric points of Parv1, Parv2 and Parv3 in grunting toadfish were 4.77, 4.58 and 4.42, respectively. In the sonic muscle, the major parvalbumin isoform was parvalbumin isoform 1 (Parv1), which comprised more than 94% of total parvalbumin, and parvalbumin isoform 2 (Pav2) comprised vi only 5% of total parvalbumin content. In body white muscle, on the other hand, the major isoform was parvalbumin isoform 2 (Parv2) which comprised 58% of toal parvalbumin. Both Parv1 (with Parv1a) and Parv3 comprised about 20%. Parvalbumin isoforms were be discussed. The result supports that Parv1 has a highest effect on the relaxation of the grunting-toadfish¡¦s sonic muscle.