In order to study the inbreeding effects, the data from different periods of Holstein cows were collected by Vahdat commpany in Isfahan in collaboration with Breeding Center of Iran during twenty one years (1368 to 1389). In addition, pedigree information from 86,481 cattle was used for review of the coefficient of inbreeding in herds of cattle in Isfahan province.In about 14.69%, 15.09% and 18.30% of the animals had unknown father, mother and parents, respectively. Base-year population for this study was taken in 1357 and the average inbreeding coefficientwas 2.33 oase-year population of 1357 as referenceopulation. The results showed that the high relatively estimate of inbreeding coefficient of total population was due to incompleteedigreeof many cows and close matings by the farmers. In the pedigree, 66.18% of the animals were inbred and their average inbreeding coefficientestimated about 3.57%. The inbreeding coefficient of the females (90.68% of total population) and males (9.3% of total population) in Isfahan were 2.33 and 2.35%, respectively. Age at first calving, calving interval, open days, and number of insemination during the years 1368 to 1388 were used to study rate of inbreeding depression on the quantitative traits. An animal model was used and inbreeding rate was included as a covariate effect. Average of regression coefficient for age at the first calving, calving interval, number of insemination and open days were estimated for every 1% increasing in the inbreeding as 0.589±0.21, 1.08±0.15, 0.16±0.55 and 0.27±12, respectively. The results indicated that the average inbreeding trended to increase with the reproductive traits. In general, this study showed that different herds have been related to the mating system, and the mean of inbreeding coefficient has gone up due to the close matings between the candidate parents. Keywords: Inbreeding rate, inbreedingdepression, reproductive traits, Holstein cows