This study comparatively analyzed the effects of water bath (WB) and ultrasonic-assisted water bath (UWB) extraction at different pH conditions on the extraction kinetics, gelling properties, rheological properties, and structural properties of grass carp fish scale gelatin. Results indicated that the gel strength of fish scale gelatin extracted by UWB was greater than that obtained by WB at pH more than 7.0. The rheological results demonstrated that UWB elevated the apparent viscosity of fish scale gelatin, but decreased the gelling and melt points. The results of structural analysis indicated that UWB resulted in a reduction in the content of α-helix and β-sheet in fish scale gelatin. Furthermore, both pH and UWB were found to alter the tertiary structure of fish scale gelatin. This study may provide novel ideas for the high-value comprehensive utilization of fish scale waste.