In order to apply spatial spectrum estimation to millimeter-wave thermal radiation array receiving system for detecting targets with superior resolution, it is needed to solve two key problems which are weaknesses of thermal signals’ energy emitted from targets and the decline of performance caused by array errors. To solve these problems, an array error model with low signal-noise ratio(SNR) was presented. In this model, the influences of amplitude and phase errors on signal source and channel noise were considered, and the perturbation range of the eigenvalues and the error distance of the signal eigenvector space of the autocorrelation matrix received by arrays were derived. Then the calibration algorithm for amplitude and phase errors based on the model was proposed, which could make the spatial spectrum estimation with high resolution be used in millimeter-wave radiation array system effectively. The effectiveness and correctness of the model are verified by the experiments.