A memory management method is used for a mobile device. The method comprises the following steps: initializing memory blocks and beginning to calculate the peak utilization ratio and the mean fragmenting ratio of the memory blocks when the mobile device is started; at the interval of time set, readjusting the configuration of the memory blocks, comprising: adjusting the memory blocks P1 and P2 of the highest and lowest peak utilization rates, adjusting the memory block P3 of the highest mean broken ratio in those of which the peak utilization rates are higher than the peak utilization ratio preset, adjusting a memory block P4 of which the size is just smaller than that of the memory block P3; and combining the rest parts adjusted into a plurality of P1 blocks. The present invention also provides a memory management system. The configuration of the memory blocks can be dynamically adjusted by the present invention according to the actual use conditions.