Abstract: A new precision measuring and calculating method about weighted factor ξ(hkl) during preparation of Harris-Mueller inverse pole figure is presented in this paper. The calculation formula obtained by using this kind of method is as following P(hkl)=I(hkl)Is(hkl)/∑ni=1I(hkl)iIs(hkl)∑m-2j=14πR2180°tg-1tgPj2tg(Pj-αj)2tg(Pj-βj)2tgPj-γj2/SB. The numerical value of ξ(hkl) calculated by LG method no longer contains the systematic error resulted by the approximated processing. The experiment results of Al-Mg-Sc-Zr alloy plate show that the precision of H-M inverse pole figure calculated by LG method has the obvious superiority over other current approximated methods.