  The Wide Field-of-View Cherenkov Telescope Array (WFCTA) and the Water
Cherenkov Detector Arrays (WCDA) of LHAASO are designed to work in combination
for measuring the energy spectra of various cosmic ray species over a very wide
energy range from a few TeV to 10 PeV. The energy calibration of WCDA can be
achieved with a proven technique of measuring the westward shift of the Moon
shadow of galactic cosmic rays due to the geomagnetic field. This deflection
angle $\Delta$ is inversely proportional to the energy of the cosmic rays. The
precise measurements of the shifts by WCDA allows us to calibrate its energy
scale for energies as high as 35 TeV. The energy scale measured by WCDA can be
used to cross calibrate the energy reconstructed by WFCTA, which spans the
whole energy range up to 10 PeV. In this work, we will demonstrate the
feasibility of the method using the data collected from April 2019 to January
2020 by the WFCTA array and WCDA-1 detector, the first of the three water
Cherenkov ponds, already commissioned at LHAASO site.
