The process br dividing the different deformation trend blocks with displacement observations includes three steps. They are datum detection, block scope told part and anomalous deformations detection in blocks. Fhe three steps are implemented by Quasi-Accurate Detection(QUAD) in the paper, In the previous two steps, the preliminary selection for Quasi-Accurate Observations (QAOs) is key. The preliminary selection is according to the size of deformation displacement for datum detection and according to the direction of deformation for block scope told part At last through an example, each implementation process is introduced simply and the detection effect of QUAD is compared with that of the robust estimation (Huber) and the statistic test. The result indicates that the three steps can be implemented successfully with QUAD and that the anomalous deformations in blocks can be detected, but the steps of the datum detection and block scope told part are failed by robust estimation, The detections of three steps are lailurc by the statistic test. The results show that the QUAD has the virtues that the location of gross errors is much accurate and the breakdown point is higher than the other two methods.