The purpose of this paper is to show the investigation on a type of unitary piezoelectric four-component cutting dynamometer. Based on piezoelectric effect of quartz crystal, such as torsion effect, transverse effect, lengthways effect and shearing effect, horizontal moment and three-direction orthogonal forces carried on the dynamometer during cutting process can be measured simultaneously. The dynamometer can be used to measure forces and horizontal moments in drilling, grinding, milling, turning. A secondary purpose is to optimize structure parameters of the dynamometer by ANSYS. The dynamometer has good performance with high sensitivity, good linearity and repeatability and low crosstalk after optimizing.