In order to study the variation law of dynamic tensile properties of phyllite under the coupling effect of water temperature, three groups of samples were subjected to 0, 1, 3, 5, 7, 8 and 11 times of temperature cycle natural cooling, temperature cycle cold water cooling and dry-wet cycle respectively. The dynamic Brazilian splitting test of phyllite samples was carried out by Hopkinson bar test device. The dynamic tensile properties of phyllite under water and temperature deterioration were studied from five aspects : dynamic tensile strain curve, dynamic peak tensile strength, dynamic elastic modulus, energy analysis and macroscopic failure. It is found that the stress-strain curve of phyllite includes extremely fast elastic deformation stage, yield deformation stage and failure deformation stage. With the increase of the number of water temperature cycles, the extreme elastic deformation stage of the phyllite stress-strain curve gradually decreases, and the strain growth rate in the yield deformation stage increases continuously. The dynamic peak tensile strength of phyllite shows a negative exponential function distribution, and the dissipation energy ratio decreases continuously. Under the condition of water temperature coupling, the peak tensile strength and dissipation energy ratio of phyllite are generally smaller than those of temperature cycle natural cooling. Under the dynamic impact, the phyllite occurs tensile failure throughout the bedding, mainly broken into 2 pieces. With the increase of the number of water temperature cycles, the main phyllite fragments undergo tensile failure along the bedding plane and shear failure across the bedding plane, and the average size of the phyllite fragments decreases continuously. Under the condition of temperature circulating cold water cooling, the average size of phyllite fragments is smaller and the decrease is the most significant.