1. A method of compensating a defective nozzle in an inkjet image forming system, comprising: detecting an occurrence and a position of the defective nozzle in a nozzle unit; analyzing image information on image data which are to be printed at a compensated position which is a position printed with the detected defective nozzle and image data which are to be printed at one or more positions adjacent to the compensated position; exchanging the image data which are to be printed at the compensated position with image data which are to be printed at one of the adjacent positions according to the analyzed image information and without adding image data; and performing printing using the exchanged image data.