Low estrus intensity might be caused by a low quality and quantity of ovum. This problem may adversity affect conception rate in Bali cows. This might be due to the insufficient of feed consumption of the animals. This study (the first step out of 2 steps proposed) aimed to evaluate estrus intensity, estrus cycle length and conception rate of Bali cows. Twenty (20) cows were used. They were injected with prostaglandin for estrus synchronization. All animals were not artificially inseminated (AI) after the onset of estrus. The estrus cows were devided into 2 groups of 10 cows. Group 1 (treatment group) was supplemented with moringa oleyfera leaf (MOL) block 0.5 kg/head/day. Group 2 (control group) was not supplemented. During estrus after the treatments. Estrus intensities were scored based on the secondary estrus signs (vaginal mucus, swallen of vulva and tail head posisition). The scores were ranging from 1 (low intensity), 2 (medium intensity) and 3 (high intensity). Length of estrus was noted and all estrus animals were inseminated. Pregnancy diagnosis were done 60 days afted the AI. During the AI, blood smples were collected for vitamin A analisis. At the MOL block groups, estrus intensity and conception rate were significantly (P<0.01) higher in compared to the non supplemented group (2.8 vs 1.9) and (80 vs 40%), respectively. Length of estrus cycle in the supplemented group tended (P<0.1) to be shorter and less variation in compared to non-supplemented group. Length of estrus cycle in the treated group was 19.5 days (18-22 days) and in the non-supplemented group was 21.5 days (16-26 days). It can be concluded that the supplementation of MOL block could increased the estrus insensity and conception rate of Bali cows.