Based on control experiments, a new series of second-order nonlinear optical polymers with fluorene moieties as isolation spacers were successfully prepared. In the polymers, the chromophore moieties were embedded into the polymer backbone with one position at the donor side, and another point in the pi bridge. Different acceptors were used to construct the push-pull structure of chromophore moieties, including nitro groups, sulfonyl groups, 3-phenyl-5-isoxazolone, 1,3-diethylthiobarbituric acid and TCF groups. The tested NLO properties of the polymer,,; demonstrated that the isolation groups with big size do not always benefit the resultant NLO effect. Also, for different acceptors, there should be different suitable isolation groups to balance the good and bad effects caused by the introduced isolation spacers. (C) 2007 Elsevier Ltd. All rights reserved.