The invention discloses a diesel engine control system. The diesel engine control system comprises a first comparer, a second comparer, a third comparer, a logical gate, a non-logic gate, a delayer, afirst selector, a second selector, a fourth selector, and an electronic control unit. The first comparer and the second comparer are used for judging the water temperature and the first limiting value and the second limiting value. The third comparer is used for judging the water temperature variation slope and the water temperature variation slope limiting value. Through the logical gate, the non-logic gate, the delayer, the first selector and the a second selector, different torque selections are provided for different temperatures and temperature change situations. The smaller value is selected based on the fourth comparer and is input to the electronic control unit. The electronic control unit can control the torque of the diesel engine based on the water temperature and the water temperature variation slope. The dynamic performance of the diesel engine is guaranteed, and the diesel engine is prevented from being damaged due to excessive high water temperature. The invention further discloses a control method.