A system capable of selecting an optimal plant cultivation method mainly includes a plurality of water supply units, a water treatment unit, a plurality of nutrition units, a reactor, a plurality of gas supply units, a liquid storage unit, at least three growth boxes, an information device. A method capable of selecting an optimal plant cultivation method allows participants of a competition in every place of the world to operate the same greenhouse facilities together at the same time, and grow the same plant or a several types of plants at the same time, latitude and location. But, every participant themselves may use the facilities provided in the greenhouse to adjust and control other growing conditions, environmental factors, cultivation methods and nutrition formulas, and the best cultivation method and nutrition formula are selected, thereby finding out the best cultivation method of the plant when the competition is over.
