The adjacent interharmonic pairs or single adjacent interhamonic symmetrical to the fundamental/harmonic component can be caused by the large-scale grid connection of renewable energy. It is usually necessary to confirm the type of adjacent interharmonics to build an accurate calculation model when estimating the frequency components in electric signal. However, the spectrum leakage interferences caused by the grid frequency deviation makes that requirement hard to achieve. Towards the problem, an effective criterion to confirm the type of the adjacent interharmonics and an accurate estimation method of the harmonics and adjacent interharmonics based on the criterion even there is frequency deviation are proposed. Firstly, the spectrum leakage interferences are suppressed to obtain the adjacent interharmonic spectral lines by analysing the relationship of the frequency deviation and spectral lines. Then, the type criterion of the adjacent interharmonics is proposed by comparing the spectrum difference between each type of adjacent interharmonics. Finally, the spectral line equation for each type of adjacent interharmonics are constructed according to the confirmed type to accurately estimate the harmonics and adjacent interharmonics. Even there is frequency deviation, the type of the adjacent interharmnics can be confirmed accurately and a more precise estimation of the harmonics and adjacent interharmonics can be achieved with the proposed method. The accuracy of the proposed method is verified by the simulation.