The planting amount is determined by farmers according to the profit of planting economic crops. Moreover, the planting profit is estimated by using the statistical methods. The relation between the planting amount and the profit is similar to a linear function. However, the straight line equation has been set by using the historical data, calculating the slope of the straight line or adopting the least squares method. Therefore, the planting amount in next year will be calculated based on the equation. In a word, the planting amount in next year will be adjusted and controlled on the basis of the calculated planting amount and the real demand in the market.