Abstract: The cooperative arrangement of gas extraction boreholes and pressure relief boreholes can effectively control compound disasters of coal and gas outburst-rock burst in deep mines. However, improper borehole spacing may induce crack propagation and collaborative borehole deformation, potentially leading to borehole interconnection and collapse that compromise gas extraction efficiency. To investigate the characteristics of crack expansion and borehole deformation in coal containing double boreholes during failure, the digital image observation experimental platform for deformation and failure of coal body was used to carry out the deformation and failure experiments on coal specimens containing different borehole spacings. The characteristic parameters, such as the surface strain fields, crack opening and shear, and borehole shrinkage were quantitatively analyzed to characterize crack expansion and borehole deformation around the boreholes. The Pearson correlation coefficient was introduced to explore the correlation of crack expansion and characteristics of borehole co-deformation under different borehole spacings. The results indicate that: ① With the increase of borehole spacing, the elastic modulus, peak strength, elastic strain energy, and stress threshold of cracks on the surface of the sample increase first and then decrease. The failure mode of the sample is characterized by the process from core failure to independent failure, and then to boundary failure. ② At initial stage of loading, crack opening and shear remain relatively stable, and small slip dislocation occurred in the left and right sides of the borehole, accompanied by limited borehole shrinkage. In the middle and later stages of loading, the cracks opening and shear continuously, and the boreholes are subjected to large stress concentration. The shrinkage of the boreholes decreases rapidly, which directly leads to the failure of the samples. ③ Pearson correlation coefficient can intuitively show the interaction between cracks. There are significant differences in the interaction of the crack expansion process of the three groups of samples with different borehole spacing. The crack openings of SH-25 mm and SH-50 mm are highly correlated, and the cracks around the boreholes on both sides tend to develop synchronously during the whole failure process. The maximum crack opening of the SH-37.5 mm has the lowest correlation, and the cracks around the hole tend to expand independently. ④ Borehole shrinkage C displays distinct correlation characteristics, the smaller spacing (SH-25mm) induces strong collaborative deformation between boreholes; the significant weak correlation between the bilateral boreholes of optimal spacing (SH-37.5 mm); the deformation correlation coefficient R on the left and right sides of boreholes with larger spacing (SH-50 mm) is negative and shows a strong correlation. ⑤ Combined with the mechanical characteristics, the law of crack propagation and the borehole deformation characteristics of the samples, the SH-37.5 mm shows better stability in the layout. Therefore, the spacing of double-prevention boreholes is 1.5 m, which can ensure that the pressure relief boreholes reduce the coal seam pressure and improve the gas extraction effect.