The SCSI command optimizing method based on PC-SAN storage devices characterizes that it is directed against the special I/O processor and the operation device, commands, operation addresses and waiting time to judge the command in every SCSI queue to see if there are repeat commands sent by different users or a same user, if the waiting time of SCSI commands is longer than the longest time stimulated by the program, if these SCSI commands are sent to a same device and addresses are close then it deletes the repeat commands, prolongs the suppertime commands and merges the adjacent commands to solve the complicated problems in dealing with SCSI commands.