Provided is a risk-control-based quantitative trend transaction decision-making system. The decision-making system quantifies the investment risk to calculate operation points of buying, selling, take profit, and stop-loss. Also provided is a decision-making method. The decision-making method provides a transaction command based on probabilistic analysis, conducts trial and error of the transaction command under the premise of risk control, provides a stop-loss value to a false command to force liquidation, provides a take profit value to a correct command, and provides a quantitative transaction or a subjective transaction. A transaction can be subjectively conducted through a quantitative transaction model to try to gain the best profit under a condition of profitability; under a condition of loss, the transaction risk should be controlled to the minimum as the transaction is strictly executed according to the quantitative decision-making system; and quantization illuminates the minimum actionable cycle of ups and downs, so that selection of the best point for profit taking and stop-loss is facilitated.