Abstract: Five methods of the molecular formula of calculated compounds consist of high resolution mass spectrometer (HRMS), high resolution mass spectrometer data(HRMS data), element analysis(EA), 13 C nuclear magnetic resonace(COM, DEPT) data( 13 C NMR data (COM,DEPT)) and three fact simularity. (1) The molecular formula of compound was supposed on the basis of precise molecular weight (M) and cycles plus double bonds (r+db) measured b HRMS. (2) The calculation method is siminary with the previous, but the hydrogen atom amounts in molecular formula have been estimated to go by decimal of precise molecular weight at first. (3) The molecular formula of compound was determined according to the precise molecular weight and cycles plus double and the elemental percentage content by HRMS and EA. (4)It was calculated to go by amounts of the various functional groups acquired by 13 C NMR. (5) On the basis of comparison between the characteristic ion mass spectra and the common molecular formula CH 3(CH 2) nCOR, the detected mo lecular formula was centified, for example, Leucomycins, Mide camycins and Shenjimycins have the common molecular formula C 35 H 56 NO 13 RR 1R 2, their differences are only the different R, R 1 and R 2.