This paper studies the observability of calibration system with a constraint movement by a constraint operator. The calibration system with the constraint movement need only simple sensing device to check whether the constraint movements are completed within an established range. However, it yields the concern about the poor parameter observability due to the constraint movements. This paper uses the QR-decomposition to find the optimal calibration configurations maximizing the linear independence of rows of a observation matrix. The number of identifiable parameters are examined by the rank of the observation matrix, which represents the parameter observability. The method is applied to a parallel typed machining center and the calibration results are presented. These results verify that the calibration system with low-cost indicators and simple planar table is accurate as well as reliable.