The idea of a slot waveguide amplifier based on erbium-doped tellurite glass is first theoretically discussed in this work. Choosing the horizontal slot for low propagation loss, the TM mode profile compressed in the insertion layer was simulated, and the gain characteristics of the slot waveguide amplifier were calculated. Combining the capacity to confine light locally and the merits of tellurite glass as an emission host, this optimized amplifier shows enhanced interactions between the electric field and erbium ions and achieves a net gain of 15.21 dB for the 0.01 mW input light at 1530 nm, implying great promise of a high-performance device.