An impact tool, comprising: a housing; a motor comprising a drive shaft that rotates about a first axis, where the drive shaft optionally rotates in a first direction or a second direction; an output shaft for outputting torque, wherein tightening torque of the output shaft to a workpiece is greater than or equal to 950 N.m (700 foot-pounds) and an impact assembly that provides an impact force to the output shaft, wherein the impact assembly comprises: a main shaft driven by the motor and rotating about a main shaft axis; an impact block supported on the main shaft and rotating integrally with the main shaft; a hammer anvil mating with the impact block and struck by the impact block; and a rolling ball connecting the main shaft to the impact block; wherein a main shaft ball groove is provided on the main shaft and comprises a first ball groove that extends spirally about the main shaft axis and is concave on an outer surface and a second ball groove that extends spirally about the main shaft axis and is concave on the outer surface; the impact block is provided with an impact ball groove that mates with the main shaft ball groove to accommodate the rolling ball, wherein the impact ball groove comprises a third ball groove that mates with the first ball groove to accommodate the rolling ball and a fourth ball groove that mates with the second ball groove to accommodate the rolling ball; and an included angle α between the first ball groove and the second ball groove is less than 117°; characterized in that the included angle α between the first ball groove and the second ball groove is less than an included angle β between the third ball groove and the fourth ball groove. a housing; a motor comprising a drive shaft that rotates about a first axis, where the drive shaft optionally rotates in a first direction or a second direction; an output shaft for outputting torque, wherein tightening torque of the output shaft to a workpiece is greater than or equal to 950 N.m (700 foot-pounds) and an impact assembly that provides an impact force to the output shaft, wherein the impact assembly comprises: a main shaft driven by the motor and rotating about a main shaft axis; an impact block supported on the main shaft and rotating integrally with the main shaft; a hammer anvil mating with the impact block and struck by the impact block; and a rolling ball connecting the main shaft to the impact block; a main shaft driven by the motor and rotating about a main shaft axis; an impact block supported on the main shaft and rotating integrally with the main shaft; a hammer anvil mating with the impact block and struck by the impact block; and a rolling ball connecting the main shaft to the impact block; wherein a main shaft ball groove is provided on the main shaft and comprises a first ball groove that extends spirally about the main shaft axis and is concave on an outer surface and a second ball groove that extends spirally about the main shaft axis and is concave on the outer surface; the impact block is provided with an impact ball groove that mates with the main shaft ball groove to accommodate the rolling ball, wherein the impact ball groove comprises a third ball groove that mates with the first ball groove to accommodate the rolling ball and a fourth ball groove that mates with the second ball groove to accommodate the rolling ball; and an included angle α between the first ball groove and the second ball groove is less than 117°; characterized in that the included angle α between the first ball groove and the second ball groove is less than an included angle β between the third ball groove and the fourth ball groove.