Gamma-ray Transient Monitor (GTM) is the fourth payload of the GECAM series, operating as an all‑sky gamma‑ray monitor in the Distant Retrograde Orbit (DRO) aboard the DRO‑A satellite launched on March 13, 2024. It carries five Gamma‑ray Transient Probe (GTP) detectors made with NaI(Tl) scintillator readout by SiPM array, covering an energy band of about 10 keV to 1 MeV. Benefiting from its deep‑space orbit, GTM achieves an instantaneously full‑sky monitoring for gamma‑ray burst (GRB), gravitational‑wave electromagnetic counterpart (GWEM), soft gamma-ray repeater (SGR), solar flare (SFL) and other high‑energy transients.