The development of organic/polymeric materials with second-order nonlinear optical (NLO) performance became more and more important, due to the increasing potential for the applications in photonic devices and many advantages over conventional inorganic crystalline materials in the last few decades, especially after 1980s. So far, the NLO polymers have developed from the initial guest-host systems, to side-chain polymers, cross-linked systems, dendrimers and dendronized polymers, and then to hyperbranched polymers and even self-assembly systems. As a result, the NLO coefficients have been improved from lower than 10 pm/V to above 300 pm/V. In this article, we would like to review the development of NLO polymers, especially some recently reported design strategies, such as "site-isolation principle", the concept of "suitable isolation group", the special effect of "isolation chromophore", Ar-Ar-F self-assembly effect, etc. (c) 2013 Elsevier Ltd. All rights reserved.