This article describes the difference of mobility between N type indium antimonide ingot and the rectaugular sample, which was cut from the ingot on the position where we want to measure the mobility of ingot. This difference exceeds the error of the measurements. Therefore we think this is due to the introduction of the mechanical damage by cutting and grinding. And at the same time it is also due to the introduction of the thermal damage by the preparation of the electrical contacts. They influence the electrical Properties of the sample studied. From the determination of the change of the electrical properties of the sample one can determine the depth of the mechanical damage thae is about 0.2 to 0.4 mm. From Read's theory of scattering due to dislocation, one can calculate the mobility, and then predict the mobility of the sample. Our experimental results agree with the theoritical prediction quite well. Therefore we believe that the mechanical damage will introduce dislocations (i.e. dislocation crack) into the sample, and they thus influence the electrical properties of the sample. From the experimental results we find the method of preparation of electrical contacts by pressing the gold wire better than that by soldering.