A gratingsimilar material sensor has been designed and fabricated for the strain measurement of the key points in the model experiment interior. Different from the conventional brick strain method of which the grating is pasted on the surface of the cube specimens, the grating used in this work is embedded into the similar material cube specimens in order to eliminate the influence of boundary effect. Through the contrast experiment, the layout process of the decoated grating in the similar material is studied. In order to verify the reliability of the sensor used in the internal strain measurement experiment, based on Saint Venant theorem, the sensor is embedded into the center of the similar material specimen with the side length of 3 times larger over the sensor to simulate the conditions of the actual experiment with the confining pressure and eliminate the boundary effect. The experimental results verify the reliability of the measurement results.