Two group chromophores with strong methoxy electron donor and CF3 electron acceptor were synthesized and reported. To investigate the effects of conjugative bond and its length between electron donor and acceptor on optical properties, thiophene ring was incorporated into the conjugated units of group B compared to group A. The results showed that the incorporation of thiophene rings could significantly enhance molecular first hyperpolarizability and permit a high thermal stability. It has been found that molecular first hyperpolarizability increased continually by the increase of bond length of group A. However, further increase of conjugated bond length between electron donor and acceptor in group B reduced the molecular hyperpolarizability. This study indicates that both the nature of the conjugative bridge and its bond length between electron donor and acceptor have inner correlation to optimize the molecular hyperpolarizability for electro-optical applications.