In this paper the authoxs took the Fuping Group for example to introduce the method of B. E. Lujinco (B. E. PyAeHxo) which used quantitative mineral- ogy calculation for inferring the chemical composition of rocks and restoring the protolith nature of metamorphic rocks. Conversion coefficients of some minerals were added with hundreds of mineral analyses. Comparing this method with the other protolith restoration methods, the authors concluded: 1 .This method is applicable for protolith restoration. Its advantages are of being economic, quick and simple in performance. 2.This method is conducive in solving some problems of protolith restora- tion which are difficult to be solved with the orther petrochemical methods. For example, in the case of some thin-bedded rocks this method may be used for calculating the mineral contents of each layer separately, restoring the protoliths nature of each layer and discussing their forming environment. 3 .The practice work indicated that this method is not quite successful for restoration of the protolith nature of amphibolitic rocks, but it is satisfac- tory for restoration of other type rocks.