The embodiment of the present application discloses a method, device and system for determining a longitudinal-to-transverse wave velocity ratio. The method includes: constructing a longitudinal wavevelocity spectrum corresponding to a data pair composed of a converted wave vertical travel time and a longitudinal-to-transverse wave velocity ratio according to longitudinal wave seismic data of a target work area; constructing a converted wave velocity spectrum corresponding to the data pair according to the converted wave seismic data of the target work area; obtaining the maximum value of thelongitudinal wave energy and the maximum value of the converted wave energy corresponding to the data pair according to the longitudinal wave velocity spectrum and the converted wave velocity spectrum respectively; obtaining a weighted scan spectrum according to the product of the maximum value of the longitudinal wave energy and the maximum value of the converted wave energy corresponding to thedata pair; and determining the longitudinal-to-transverse wave velocity ratio of the target work area according to the scan data corresponding to the converted wave vertical travel time in the weighted scan spectrum. With the various embodiments of the present application, the accuracy of the determination of the longitudinal-to-transverse wave velocity ratio can be improved, thereby improving the processing and interpretation efficiency and accuracy of the converted wave seismic survey data.