Sperm preparation technique is a very crucial step in the success of IUI.It separates highly motile functional sperm with normal morphology in high percentage and removes seminal plasma that contains prostaglandins and cytokines and antigenic or infectious matter along with defective and nonvital sperm and debris.
The technique required for IUI : centrifugation of human semen to separate spermatozoa from seminal plasma.Some of the are superior to all other techniques:the density gradient centrifugation and the glass-wool filtration technique.They impove the number of morphologically normal and grade A motility and with normal chromatin condensation in the prepared sample.

Addition of substances in sperm preparation: pentoxyphylline,kallicreine and follicular fluid,antioxidants,platelet-activating factor (who may have a stimulatoru effect on centriole-intact spermatozoa,enhancing their motility and fertilization success and resulting in improved pregnancy rates).