We obtained the moment magnitude of 218 microearthquakes recorded by a microseismic network deployed near the third bore hole of Wenchuan Earthquake Fault Scientific Drilling(WFSD-3)by fitting the displacement spectra. Meanwhile,we derived the local magnitude of these microearthquakes based on the calibration function of the Specifications of Earthquake Observatories(Calibration function GF)and the calibration function of Li Xuezheng et al(Calibration function LXZ,2003),respectively. Then,we extracted the relationship between the two types of local magnitude and moment magnitude of microearthquakes with linear regression,and discussed its implications. The b-value in the relation M_W=a+bM_L reflects the relation between the stress drop Δσ and the seismic moment M₀ of microearthquakes,that is,b=1/(1+γ) equivalent to the relationship between the static stress drop Δσ and the seismic moment M₀ is Δσ∝M₀^γ. The result in this study is corresponding to b=1. Due to the differences between the static and the dynamic stress drop are not too large,we can also deduce the same relationship between the seismic moment and the reduced energy,apparent stress as that between the seismic moment and the stress drop. Therefore,we are able to infer the relation between the seismic moment and the stress drop,reduced energy,as well as apparent stress from the value of b in the formula M_W=a+bM_L. The local magnitude based on the calibration function LXZ is more close to the energy magnitude,and all of the two in the fitting relation M_W=a+bM_L have the same value of b, almost equal to 0.5,which is not only corresponding to the relationship between the stress drop and the seismic moment,but also suggests that the calibration function LXZ is superior to the calibration function GF from the viewpoint of energy.