Vortex-induced vibration (VIV) is one of self-excited vibration with limited amplitude, usually occurring on long and slender structures with lower damping. A nonlinear method based on Scanlan's nonlinear vortex-induced vibration model is proposed in this paper for interpreting the test results of section model into prototype structure. Partial correlation of vortex-induced aerodynamic force along span is considered in this method, and the identifying method of parameters in the semi-empirical mathematic model is improved. Validity of proposed theory is confirmed by section model tests and observed results in field of a long-span suspension bridge. (C) 2013 Elsevier Ltd. All rights reserved.