Metastable helium Lidar detects the metastable helium density in the thermosphere and exosphere by emitting 1 083.0 nm laser, which is locked at the resonance lines of metastable helium atoms. The detecting range can cover the altitude from 200 km to 1 000 km. In this height range, metastable helium density was quite low, usually lower than 1 cm-3. University of Science and Technology of China (USTC) was now developing metastable helium resonance fluorescence lidar based on six 1 m-diameter telescopes array and high power 1 083 nm pulse laser. The effective area of this telescope array was 4.8 m2; The high power pulsed 1 083 nm laser employed optical parametric oscillation (OPO) and optical parametric amplification (OPA) techniques, used 532 nm pulses as pumping laser, and emited single mode 1 083 nm pulses with a frequency bandwidth of300 MHz; The receiving system employed a InGaAs single-photon-counting detector with deep cooling (-120 ℃), the quantum efficiency was higher than 30% accompanied with a dark count lower than 100 s-1; The background noise was filtered by series-connecting of interference filter and FPI ultra-narrow-band filter. The final filtering bandwidth was 10 GHz and the peak transmittance was 55%. Based on the above key performance of the system, the SNR would be about 400 in the strong-signal season and 10 in the weak-signal season.