The invention discloses a steel ball mill for coal crushing. The steel ball mill comprises a milling rod and a milling body, and is characterized by further comprising a connecting component and steel balls; the connecting component is fixed to the bottom of the milling rod and connected with the top face of the milling body through four screws; the milling body is arranged to be of a hollow structure, and the multiple freely-moving steel balls are placed in the milling body; and the milling body comprises a cylinder component and an arc component, and the arc component is arranged at the bottom of the cylinder component and is arranged to be a spherical segment with the bottom end being a circular plane. According to the steel ball mill for coal crushing, the shearing force of the arc bottom is much larger than acting force applied by the hand of people to holding the milling rod, and therefore the labor intensity of a sample preparation person can be reduced; during crushing, the maximum shearing force of the arc bottom is concentrated on the contact part of the mill bottom and coal briquettes, the crushing speed of the coal briquettes is increased, and the labor productivity is improved; and when the coal briquettes are crushed through the steel balls in a milling manner, contact grinding rather than striking crushing is carried out, and therefore sample splashing is not likely to occur.