In the MIMO based terahertz three-dimensional imaging radar for human security screening, the speckle effect affects the detection and recognition performance of hidden contraband seriously. For this reason, effective suppression of terahertz holographic speckle is demanded urgently. By using the angle based degree of freedom for speckle suppression obtained by the target rotation, a terahertz holographic radar speckle suppression method based on multi-look correction of correlation angle was proposed. Meanwhile, the angle sensitivity of the target scattering was carefully considered. In theory, the normalized covariance expression of the holographic radar speckle intensity under the relevant angle illumination was derived, and the speckle contrast after multi-view processing was given. Experimentally, based on the fast speed of the 340 GHz MIMO based imaging system, single-look images of low-speed rotating target were obtained. The imaging space rotation correction, target registration and multi-look processing were performed on each single-look image under the relevant viewing angle. The speckle contrast of the averaged reconstructed image was reduced to 44% of a single reconstructed image. The processed speckle was effectively suppressed with distinct target contour and details. The proposed method can effectively suppress speckle noise and achieve image enhancement without increasing system complexity.