Using monosubstituted benzene as a model and presuming: (1) the conjugative effect of meta - position is prohibited; (2) the transmit factor of induction effect in the conjugative system is 1/2, the experimental formula for the conjugative effect parameters can be expressed as follows: Where △δp and△δm refer to the deviations of ^1^3C NMR chemical shifts of para - and meta - positin of monosubstituted benzenes with respect to unsubstituted parent respectively. δp and δm refer to the ^1^3C NMR chemical shifts for para - position and metal - position respectively. Using the formula, conjugative effects parameters for 559 groups are calculated, and the results agree well with the observed values in the literature.

Key words: GROUP, CONJUGATIVE EFFECT, C13 NMR SPECTROMETRY, CHEMICAL SHIFT, BENZENE P