The invention discloses a seed laser injection active optical fiber rod single-mode laser. The laser comprises a pumping source (2), a single-mode seed fiber laser (1), a rare earth ion-doped opticalfiber rod or optical fiber (5), wherein, pumping is performed on the rare earth ion-doped optical fiber rod by the pumping source (2), one end of the optical fiber (5) is connected with an output endof the single-mode seed fiber laser (1); the optical fiber (5) with a cladding of the other end thereof partly or entirely removed is placed into a cladding (4) of the rare earth ion-doped optical fiber rod or a hole inside a core (6) of the rare earth ion-doped optical fiber rod, and then heat treatment is performed on the rare earth ion-doped optical fiber rod to ensure that the hole is free from air gap. The optical fiber (5) and the core (6) of the rare earth ion-doped optical fiber rod are strongly coupled, which causes the rare earth ion-doped optical fiber rod to resonate on the laser wavelength produced by the single-mode seed optical fiber laser, thus realizing the ultra-bright high power output of the single-mode laser.