Abstract: In this paper the contribution of two constitutional factors in the sequence of EV copolymers to the ¹³C NMR chemical shift of methylene and methine in copolymer chain structure is describedsy stematically.
The SCS method and the semiempirical method are combined perfectly. The physical meaning of parameters δ_LE and δ₀ are explained clearly. On the basis of the parameter δ_t which is the chemical shift of the trans conformation of polyethylene chan, formula(6) is suggested for the calculation of ¹³C NMR chemical shift of methylene and methine in EV copolymers.
δ_c=δ_t +Σn_iS_i +ΣP_jγ_j
Based on formula (6), the sequences of polyethylene, polypropylene and ethylenevinyl copolymers are discussed respectively.

Key words: Ethylene-Vinyl Co polymers, ¹³C NMR, Substituent chemical shift method(SCS), Semiempirical method, Chain structure