Near trapping is a kind of strong hydrodynamic interaction phenomenon in a regular array under specific incident wave conditions, which causes the excitation force on the structures in the array to change suddenly. In this paper, based on linear potential flow theory, the effects of near trapping on the hydrodynamic interaction and wave-power extraction characteristics of linear periodic arrays composed of the oscillating float type wave energy converters are studied by using the higher-order boundary element method in a frequency domain. The parameters considered include the separation spacing, number of devices, and incident wave direction. It is found that the near trapping significantly reduces the overall wave-power extraction, especially for the cases with a large number of devices, and changes the trend of the power distribution. The occurrence of the near trapping phenomenon depends on the ratio of the separation spacing to the wavelength and the incident wave direction. The results highlight the effective layout of linear arrays under the influence of near trapping, which not only ensures the total production power, but also reduces the power difference among wave energy converters.