A multi-channel microwave interferometer can measure plasma density radial profiles in a single plasma shot. It has six observing channels for measuring the radial electron line integrated density profile. The multi-channel microwave interferometer has been reconstructed for improving the signal intensity increase. We set a spherical mirror between the probe beam transmission horn and the injection port window of the multi-channel microwave interferometer. The insertion of spherical mirror makes signal intensity in all measuring channels to be improved. Then, we can successfully obtain the radial electron density profile in a single plasma shot.