The objectives of this study were to evaluate the effect of temperature-humidity index [THI] on body temperature change and presynch-ovsynch synchronization protocol on high producing dairy cows in summer season. The study was conducted on a commercial dairy farm. Approximately 6 weeks postpartum, ninety healthy multiparous [Average parity 4.39± 0.7] Holstein cows with average milk production 11427 ±700 L per previously 305 d were randomly assigned to four groups. The treatments were consisted of: (1) use of synchronization protocol (2) without synchronization protocol cow's body temperature was registered using rectal or rumen temperature measuring method. rectal temperature was recorded by digital thermometer in hottest hours of day and the ruminal temperature automatically measured by the thermal sensor bolus located in rumen in different hours. Standard method of presynch-ovsynch is used for estrus synchronization. The results showed ruminal and rectal temperature was affected by THI [p 0.05]. The maximum of THI was 78.46 during experiment and the maximum temperature of rumen and rectum were 39.25 and 38.89, respectively. The correlation of rectal and ruminal temperature was relatively high [R=0.55]. There was no effect of synchronization protocol on number of insemination and open days [P 0.05]. The average of open days in the group which received protocol and no received protocol was 146.28 and 146.70 days, respectively. The average of service per conception was 2.41 and 2.40 for received protocol and no received protocol group, respectively. The treatments had no effect on pregnancy rate at different time after calving, first services conception rate and the cumulative pregnancy rate [P 0.05]. It was concluded that the thermal sensor bolus are profitable for dairy cow body temperature detection and it can precisely investigate some of physiological variation. On the other side, presynch-ovsynch protocol had no effect on efficiency of reproduvtive of high production dairy cow in summer season. Keywords : THI, Body temperature, Dairy cow, Hormone, Timed artificial insemination, Reproductive performance, Dairy cows