Bacterial contamination reduces the semen quality, semen preservation, and cause of disease spread as well. Sperm fertility is essential factor of reproductive performance in swine. Sperm fertility is affected by semen quality such as sperm motility, abnormality, morphology, and rate of bacterial contamination. This study was conducted to determine the relationship between elapsed time after semen preservation on the changes of bacteria and semen quality. Semen was diluted with BTS extender without antibiotic for 7 days and sperm parameter and fertility were measured. Sperm motility was measured by CASA and total bacteria number was counted after 22 24 hr incubation from counting agar plate in which sperm dilute to 10 106 in 0.9% saline solution and inoculate to agar. Acrosomal integrity was measured by Chlortetracycline (CTC) staining. CTC patterns were uniform fluorescence over the whole head (pattern A), characteristic of uncapacitated acrosome-intact spermatozoa; fluorescence-free band in the post-acrosomal region (pattern B), characteristic of capacitated acrosome-intact spermatozoa; and almost no fluorescence over the whole head except for a thin band in the equatorial segment (pattern C), characteristic of acrosome reacted spermatozoa. Total number of bacteria was significantly increased (p<0.0001) 3 days after preservation. Sperm motility, viability, and morphological abnormality on elapsed time after preservation were lower from 5 (77.24±6.47, p<0.001) and 7 days (77.24±6.47, p< 0.001) after preservation compared to 1 (15.71±7.18) and 3 days(18.39±7.22) after preservation, respectively. Sperm viability was significantly lower (53.25±35.03, p<0.0001) at 7 days after preservation. Mohological abnormality of sperm was lower (p<0.001) at 1 (15.71±7.18) and 3 (18.39±7.22) days compared to (5 21.84±7.91) and 7 (22.59± 9.93) days after preservation. Acrosomal integrity and capacitation rate (pattern A) were significantly lower (p<0.001) from 5 days after preservation.