Abstract In order to detect ship in the spread sea clutter caused by ionospheric disturbance, algorithms of short coherent integration time (CIT) are used in over-the-horizon radar system. Here, ECVC (Estimate Clutter Via Correlation) algorithm is employed to provide higher resolution to detect ship of slow radial velocity. The following two topics are discussed: (1) the model of sea clutter and ECVC algorithm; (2) the detection results of ECVC, compared with Root, SVD (Singular Value Decomposition) and EVD (Eigen-Value Decomposition). Simulation and experiment results demonstrate the usefulness of the proposed approach.