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(Beltsville Thawing Solution) 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 $10{sim}10^6$ 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 F), characteristic of incapacitated 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 AR), 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 ($77.24{pm}6.47$, p<0.001) and 7 days ($77.24{pm}6.47$, p<0.001) after preservation compared to 1 ($15.71{pm}7.18$) and 3 days($18.39{pm}7.22$) after preservation, respectively. Sperm viability was significantly lower ($53.25{pm}35.03$, p<0.0001) at 7 days after preservation. Morphological abnormality of sperm was lower (p<0.001) at 1 ($15.71{pm}7.18$) and 3 ($18.39{pm}7.22$) days compared to 5 ($21.84{pm}7.91$) and 7 ($22.59{pm}9.93$) days after preservation. Acrosomal integrity and capacitation rate (pattern F) were significantly lower (p<0.001) from 5 days after preservation. Based on the data we obtained from this study suggested that semen preserved more than 5 days without antibiotic would not recommend use for artificial insemination.