In the three-dimensional space

the conventional strain state is expressed by three normal strains and three shear strains. Therefore

six strain gauges at least are required to determine the strain state of a point. Based on the strain state theory

a contacting three-dimensional strain rosette that can measure strain in concrete or geomaterials is developed. The device is made up of six strain gauges

and the layout of strain gauges must meet a special condition. According to the relations of components of strain between representations for the conventional strain and the linear strain in an arbitrary direction

transition matrix is built to bridge relationships between the test results and the traditional strain state. Subsequently

the solution qualification is derived and expatiated in order to illustrate the layout of the six strain gauges. The two schemes

namely the orthogonal tetrahedron and the normal tetrahedron

are studied in detail after considering the construction convenience

rational and logical methods are constructed. The tests on the device itself and further on a rectangular shaped sample made of mortar show that the two three-dimensional strain rosette is reasonable and convenient to measure the strain state of concrete

rock and soil in engineering.