A new process to produce multicrystalline silicon (Si) thin film by a solution growth method using copper-Si solution was designed and its manufacturing cost was evaluated. In order to reduce the cost, it is necessary to grow the Si crystal on a low-cost substrate. The feasibility of this was experimentally demonstrated by applying a new nucleation method of silica reduction by aluminum on the substrate. A process with a high production rate could be designed by the film growth model constructed using the experimental result of the Si diffusion coefficient in the solution. In the process, continuous Si film growth on alumina substrate from a supersaturated solution occurs when the solution is cooled down from 1,000degreesC to 800degreesC. The substrate is transferred at 20 mm/s through the temperature gradient of 25degreesC/m. The production cost of the Si thin film was evaluated for the case of solar cell production with an annual rate of 1 G W-P, by using the costs of raw materials, electricity, equipments, buildings, and labor. The estimated cost was Y6.3/W-P, which was much lower than the substrate production cost by the conventional cast process of multicrystalline Si.