The invention discloses an orthogonal beam line observation system for offshore three-dimensional seismic exploration. The orthogonal beam line observation system is provided with a plurality of seismic receiving lines which are distributed transversely at equidistance along a left-right direction, each seismic receiving line is called an arrangement, a plurality of seismic receiving channels which are distributed longitudinally at equidistance are arranged on each arrangement, each seismic receiving channel is provided with a detector, a plurality of shot groups are arranged at the central positions of the outer sides of the plurality of arrangement combinations, each shot group has a plurality of shot points, the shot points are distributed transversely at equidistance along the left-right direction, the shot points roll along the directions of the seismic receiving lines at equidistance in operation, and one seismic receiving line at the outermost end of one side of the arrangement combinations rolls along its vertical direction to the outer side of another seismic receiving line at the other end to form a new arrangement combination. The orthogonal beam line observation system has obvious advantages in the aspects of coverage times, shot-geophone distance distribution, azimuth angle distribution and construction efficiency.