The deformation measurement system was built with a CCD camera and a high-speed camera. Experimental tests were conducted on rectangular granite specimens with pre-cracks of mode-I under different loading rates. The speckle images captured in the process of experiments were analysed by the digital speckle correlation method (DSCM). We studied the speed of crack growth

crack-tip opening displacement

crack tip opening angle and crack stress intensity factor (SIF) of granite specimens with pre-cracks of mode-I under different loading rates. The initial speed of the crack growth of granite specimens increases linearly with the loading rate. With the increase of loading rate

the maximum speed crack increased rapidly at first and then slowly. At different loading rates

the crack-tip opening displacement of granite specimens showed three stages of evolution: nonlinear slow growth，rapid growth

and linear growth. In the linear growth stage

the slope of the curve increased with the increase of loading rate. With the increase of loading rate

the initial crack opening angle of granite specimen decreases gradually and then stabilises to 0.1°～0.13°. Before the initial fracture of granite specimens

the SIF value increased exponentially with the increase of loading rate.