  We revisit the proton emitter $^{149}$Lu utilizing the recently developed
triaxial relativistic Hartree-Bogoliubov theory in continuum (TRHBc). By
incorporating the microscopic nuclear structure properties from the TRHBc
theory into the WKB approximation, we successfully reproduce the measured
proton-emission half-life of $^{149}$Lu within experimental uncertainties. A
triaxial ground state characterized by ($\beta=0.17,\gamma=31^\circ$) has been
clarified for $^{149}$Lu. The inclusion of triaxiality significantly changes
nuclear density distributions and potentials, which results in enhanced binding
of both the nuclear system and the proton-emitting orbital. As a result, a
slightly extended half-life for the proton emission of $^{149}$Lu is achieved
after considering triaxial deformation degrees of freedom.
