A measurement system has been designed and built for testing a strain of corn grain in mass. A method of measurements has been proposed. The effect of moisture content on corn grain strain measurement results was shown. Testing was carried out on two corn hybrids: Kb-270 and Beko-210 and for four different cylinder volumes at application of 6.8 MPa maximum stress for straining grain in mass. Results of tests have been statistically elaborated and graphically demonstrated in the form of regression curves.