The chemical shift data of natural flavone derivatives was systematically studied by mathematical models. The resultls indicate that the increments of carbon-13 NMR chemical shifts between flavone derivatives and their parent have better additive and degradative rules: additive δc(k)=B(k);degradative So carbon-13 NMR chemical shifts of compounds can be calculated and predicted using presented formulas.The calculated results show that the derivations between calculated values and found values are less than 2...