To investigate the phased mechanical response characteristics of the splitting process in dry and water-saturated siltstone. A systematic method for dividing the stress-strain curve during the rock splitting process is established to analyze the stage-specific response characteristics of stress and strain as well as their corresponding mechanical mechanisms by conducted the Brazilian splitting test. The results indicate that water significantly influences the stress evolution path and the strain development path during the Brazilian splitting process of siltstone. Specifically, the compaction stress, yield stress, peak stress and unloading stress of water-saturated samples decreased to 62.68%, 50.17%, 48.90% and 68.24% of those in dry samples, respectively. The proportion of stress in the compaction stage increased by 28.50%, while that in the elastic stage decreases by 19.60%. Additionally, the proportion of stress in the yield stage decreases by 41.35%, the stress in the failure stage attenuation decreases by 11.99%. The average values of compaction strain, yield strain, peak strain and unloading strain of water-saturated samples decrease by 4.41%, 19.26%, 20.17%, and 17.39% compared to dry samples, respectively. The proportion of strain in the compaction stage increases by 20.38%, whereas the proportions in the elastic and yield stages decrease by 29.64% and 36.93%, respectively. However, the failure stage increased by 347.73%. The water-saturated reatment process enhances the plastic behavior during the splitting process. Moreover, the water-saturated reatment reduces the bending energy index of siltstone by 73.77%, effectively mitigating the bursting liability.