A deterministic reconstruction and prediction model for nonlinear long-crest waves based on buoys is proposed. In this model, the quasi-Newton method is used to iteratively optimize the amplitude and phase of free waves, and the second-order nonlinear model is adopted to simulate the evolution of waves. The numerical model is validated through the experiments. In the sea states with wave steepness lower than 0.1, the long-crest irregular waves can be accurately reconstructed and predicted by the second-order model. The linear model excludes the influence of nonlinear wave-wave interaction; therefore, it cannot accurately reconstruct and predict the phase and amplitude of waves, and the error increases with the wave steepness. Compared with the linear model, the second-order model shows a better wave reconstruction and prediction accuracy. In addition, the predictable zone based on multiple buoys is larger than the sum of the predictable zone computed based on each single buoy. The predictable zone increases with the number of buoys.