Large High-Altitude Air Shower Observatory (LHAASO) has one square kilometer array of scintillator detectors and muon detectors, 18 Imaging Atmospheric Cherenkov telescopes and a 78,000 square meter Water Cherenkov Detector Array. LHAASO located at very high altitude
(around 4410 m a.s.l.) in China. Multi-parameter observation of showers allows to measurement the energy spectrum, elemental composition and anisotropy with high resolution, which give us an excellent opportunity to understand the origin, acceleration and propagation of ultra-high energy cosmic rays. The 1/4, the 1/2, the 3/4 LHAASO array have started running in September 2019, in January 2020, in December 2020 respectively. A preliminary result of absolute energy scale
and the prospect of the energy spectrum, elemental composition of LHAASO experiment will be reviewed in the paper. The method of calibrating the ground-based detector with the displacement of Moon shadow is preliminarily established by LHAASO. Combined with the shower information measured by the three type of detectors of LHAASO, the pure proton energy spectrum will be obtained event by event. Accurate measurement of the position of the cosmic proton knee is very
important to reveal the acceleration mechanism of ultra-high cosmic rays. This will be achieved by LHAASO in the near future.