The invention discloses a continuous production method and line for a variable-thickness profile. Hot-rolled and pickled or cold-rolled equal-thickness strip steel is used as a raw material, all processes from rolling to surface coating to forming and cutting and the like of the strip steel are completed on line, production processes such as uncoiling, welding, variable-thickness rolling, degreasing, on-line heat treatment, online coating, flattening, roll-in forming, cutting and stacking are integrated, and the continuous production method is used for the fully-continuous automatic production of the variable-thickness profile. By using the continuous production method disclosed by the invention, the continuous production and coating of the variable-thickness profile can be realized, the defects of high production cost, high labor intensity, continuous production incapability and surface coating incapability of the existing variable-thickness profile are overcome, the production efficiency of the variable-thickness profile is greatly increased, and the favorable economic benefit is obtained. By using the continuous production method, a single or partially continuous production process in the prior art can be replaced, the production process of the variable-thickness profile can be simplified, and the continuous production of the variable-thickness profile can be realized.