The invention discloses an automatic releasing device and method of a color steel tile coil on a construction site, and belongs to building construction devices and methods thereof. The automatic releasing device is characterized by further comprising a releaser 2 and supports 3; connecting rods 2-5 are correspondingly installed on a shaft sleeve 2-4 of the releaser 2, coil supporting rods 2-8 are arranged on the front connecting rods 2-5 and the back connecting rods 2-5 which are located on the same sides, the releaser 2 is installed on the supports 3, speed controllers 3-5 are installed between a rotating shaft 2-1 of the releaser 2 and bearing beams 3-3 on the supports 3 respectively, and coil stop blocks 3-6 are correspondingly installed on slant support bodies of the supports 3. The automatic releasing method of the color steel tile coil on the construction site includes the steps that 1, the coil supporting rods are contracted and sleeved with the coil; 2, the coil supporting rods are stretched to support the coil; 3, the coil is installed on the supports to be in place; 4, the releasing speed of the coil is controlled; 5, shifting of the coil is controlled; 6, the coil is released, and color steel tiles are manufactured. The labor efficiency and the product quality are improved, and potential safety hazards are reduced.