An operating method, an operating system and a resistance random access memory (ReRAM) are provided. The operating method includes the following steps. A write voltage and a write current are set at a first predetermined voltage value and a first predetermined current value respectively. The write voltage and the write current are applied to a memory cell of the ReRAM for writing. Whether the write current reaches a second predetermined current value is verified, if a read current of the memory cell is not within a predetermined current range. The write current is increased, if the write current does not reach the second predetermined current value. Whether the write voltage reaches a second predetermined voltage value is verified, if the write current reaches the second predetermined current value. The write voltage is increased, if the write voltage does not reach the second predetermined voltage value.