The invention provides a sub-azimuth first arrival data volume acquisition method and device. The method comprises steps: according to an acquired geophone file and a shot point file, a geophone permutation index file corresponding to shot points is built; according to the shot point file and a pre-defined sub-azimuth starting angle and a termination angle, a shot point starting line and a shot point termination line corresponding to the shot points are built; according to the geophone permutation index file corresponding to the shot points, a starting intersection point and a termination intersection point between an effective geophone line corresponding to the shot points and the shot point starting line and the shot point termination line are acquired; according to the starting intersection point and the termination intersection point, effective geophones in a starting angle and termination angle range in the effective geophone line are acquired; and first arrival data correspondingto the effective geophones are acquired, and a sub-azimuth first arrival data volume is built according to the first arrival data. By using each embodiment of the invention, the calculation amount for acquiring the sub-azimuth seismic first arrival data is reduced, and the seismic data processing speed is improved.