Neutral number density and plasma properties measurement system have been developing for investigateing vacuum facility effects on electric propulsion performance. Neutral atom number density in a vacuum chamber in high vacuum condition was measured by means of laser Rayleigh scattering technique. The results shows the minimum detection limit is less than 0.1 Pa. Plasma parameters, electron number density and electron energy distribution function, downstream of a microwave dishcarg neutralizer were successfully measured by means of laser Thomson scattering technique. The result shows an electron temperature of 1.8 eV and an electron number density is 2.2×1017 m-3 11 mm downstream of the neutralzier.