An input/output delay optimization method, used in an electronic system comprising a host controller and a memory device. The method comprising: switching the memory device from a first mode to a second mode a high power consumption mode of the memory device; transmitting one or more first read commands to the memory device, wherein the one or more first read commands are transmitted according to different output delay values; determining an optimized output delay value according to the response status of memory device for the one or more first read commands; transmitting one or more second read commands to the memory device, wherein the one or more second read commands are transmitted according to the optimized output delay value; receiving a known data from the memory device according to different input delay values; and determining an optimized input delay value according to the correctness of the received known data.