The electronic structure and optical properties of N-doped β-Ga2O3 and N-Zn co-doped β-Ga2O3 are investigated by the first-principles calculation. In the N-Zn co-doped β-Ga2O3 system, the lattice parameters of a, b, c, V decrease and the total energy Etotal increases in comparison with N-doped β-Ga2O3. The calculated ionization energy of N-Zn co-doped β-Ga2O3 is smaller than that of N-doped β-Ga2O3. Two shallower acceptor impurity levels are introduced in N-Zn co-doped β-Ga2O3. Compared with N-doped β-Ga2O3, the major absorption peak is red-shifted and the impurity absorption edge is blue-shifted for N-Zn co-doped β-Ga2O3. The results show that the N-Zn co-doped β-Ga2O3 is found to be a better method to push p-type conductivity in β-Ga2O3.