In the present work, we demonstrate that both GaBi3 and InBi3 monolayers are Quantum Spin Hall insulators. Here, the electronic band structures and edge states of the two novel monolayers are systematically investigated by first principle calculation. Our analysis of the band inversion and Z2 number demonstrate that both GaBi3 and InBi3 are promising 2D TIs with large gaps of 283meV and 247meV, respectively. Taking GaBi3 as example, it is illustrated that the edge states are impacted by SOC and finite size effect. In addition, it is found that the compression and tension totally affect differently on the edge states. Finally, the electron velocity is studied in detail, which is highly important in the manufacturing of spintronics device.