注水算法是根据某种准则，并根据信道状况对发送功率进行自适应分配，通常是信道状况好的时刻，多分配功率，信道差的时候，少分配功率，从而最大化传输速率。本文运用matlab通过对注水算法在mino系统中的三种不同的情况下进行了仿真，比较出在小信噪比时，相同信噪比下利用CSI的功率注水算法获得容量优于未知CSI的平均功率分配算法；相同容量下已知CSI信噪比比未知CSI时的信噪比小3dB.当信噪比增大到一定程度时，功率注水算法所获得的信道容量将收敛到平均功率分配的信道容量。-Water flooding algorithm is based on certain standards, and according to the channel condition to adaptive allocation of sending power, usually is a good moment, channel situation more distribution power, channel is poor, less power distribution, so as to maximize the transmission rate. This paper USES matlab based on water flooding algorithm in Austin system of three different cases are simulated and compared in small SNR, under the same SNR use CSI power allocation algorithm for capacity is superior to the average power allocation algorithm of unknown CSI　Same capacity known CSI signal-to-noise ratio than the unknown CSI small signal-to-noise ratio of 3 db. When the signal-to-noise ratio increases to a certain degree, the power allocation algorithm for channel capacity will converge to the average power distribution channel capacity.