In order to enhance the radiation spectrum signal of laser-induced glass plasma, a hemispherical cavity which was made of glass fiber with a diameter of 10 mm was used to confine the plasma. The spectrum signals with confinement and without confinement were compared. Since the focusing of the laser has a great influence on the properties of the glass plasma, the focusing position of the laser in the sample was first optimized. The results show that when the sample surface is 3 mm above the focal plane of the lens, the spectral singnal from the laser-induced glass plasma was the strongest. Then the temporal evolution of spectral intensity under unconstrained and spatially constrained by a hemispherical cavity with the inner diameter of 10 mm was studied. The time evolution of the enhancement factor og the spectral intensity was analyzed. The results show that the spectral lines with confiment presents an enhanced phenomenon in the period of 6~15 μs after plasma generation. And the degree of enhancement of spectral lines with different energy levels is different. The maximum enhancement is achieved when the acquisition delay is 10 μs. Finally, the effect of laser energy on the enhancement of plasma radiation was studied. The results show that with the increase of laser energy, the enhancement factor of the spectral line is gradually increased. When the laser energy exceeds 170 mJ, the spectral enhancement effect begins to decrease.