The present study aimed to improving the conception rate in Egyptian buffaloes during hot summer season via increasing the number of buffaloes that are service by implementing the fixed-time natural service protocol of ovsynch without the need of estrus detection with or without injection of antioxidant (vit E+Sel). A total of 40 buffalo cows suffering from postpartum anoestrus for 4-6 months with inactive ovaries, 3-8 years old and 1-6 parities were used. Animals were divided into four comparable groups, each group of 10 buffalo cows, and treated by GPG-GS, GPG-VS, GPG-S and GPG-W protocols of fixed time service. The conception rate was 70, 50, 30 and 70% for GPG-GS, GPG-VS, GPG-S and GPG-W, respectively. Also, the present study did not reveal any significant difference in  concentration of serum progesterone between different groups on days 0, 7 and 9 before natural service, but the difference appeared more prominent on days 8 and 18 after natual service. From the present study, it can be concluded that the GPG protocol of fixed time service induces more obvious improvement in the conception rate of buffaloes with the reinjection of GnRH on the day 8 after natural service during the summer months and without reinjection of GnRH during the winter months; injection of Vit.E-Selenium induces little improvement the conception rate when compared to the non-injected group.