A method and a device for acquiring biomechanical parameters based on an ultrasonic elastomyogram are provided, wherein the method includes: synchronously collecting a dynamic myodynamics image sequence and a dynamic elasticity image sequence of a single skeletal muscle under continuous stretching; acquiring a myodynamics parameter corresponding to each myodynamics image in the dynamic myodynamics image sequence and an elasticity modulus value corresponding to each elasticity image in the dynamic elasticity image sequence respectively; and generating an ultrasonic elastomyogram curve with the myodynamics parameter as the abscissa and the synchronized elasticity modulus value as the ordinate, and estimating a muscle biomechanical parameter based on the ultrasonic elastomyogram curve. Dynamically changing biomechanical parameters can be obtained, and the obtained muscle biomechanical parameters have relatively high accuracy.