An operation method of a memory system includes sending, by a controller, a first scanning command to a memory and determining a valley voltage by scanning a plurality of memory cells. The valley voltage is determined according to a count of memory cells corresponding to different threshold voltages in a preset threshold voltage interval, the count of memory cells corresponding to the different threshold voltages being obtained by scanning the plurality of memory cells, the valley voltage being a threshold voltage corresponding to the minimum count of memory cells in the threshold voltage interval. The operation method includes sending, by the controller, a first read command to the memory, the first read command being used for instructing the memory to use the valley voltage as a reference read voltage to read target data. The operation method also includes reading, by the memory, the target data according to the valley voltage.