Olive leaf spot disease (OLS) is known as the most important disease of olive trees in Tarom county of Zanjan province and it appears as epidemic each year in most part of the county. Lack of its control imposes economic loss to the region's olive growers. In the severely infected areas, the disease control is possible only by using fungicides. The effects of 3 basic factors of temperature, rain and relative humidity (RH) in the epidemic extension of OLS is obvious but the effects of other parameters such as fertilization and bearing have not been considered yet. Therefore, this research tried to study the role of the above mentioned factors on the infection rate of olive trees to the OLS disease. For this purpose, in one of the olive gardens in Tarom, which was managed under the extension-research plan, 40 olive trees were chosen and was studied for 3 succession years (2016, 2017 and 2018). The chosen trees were Zard variety (native and most cultivated variety), fruitful and 25 years old and were in their bearing year. 20 trees out of 40 received ordinary fertilization (foliar fertilization and fertigation) according to the routine olive fertilization plan of the area. But the remaining 20 trees were not fertilized. In the mention garden, no fungicide were used during the survey period. The experiment was conducted in randomized complete block design. Treatments were performed on the same trees. Sampling was carried out to determine the infection rate according to Obanor et al. (2008) method in 21 November and 21 April of each year. The results were transferred to the Excel software and to calculate the average and to compare and analysis the average, the SAS (ver 9.1) was used. The results of the comparison of the average indicated that the fertilization role in the reduction of olive trees infection rate of had been more obvious than biennial bearing role. Final infection rate average (results of 21 April) of 3 year fertilized trees was 16.1% less than the non-fertilized trees (70.6% vs 86.7%). However, the average of olive trees infection percentage in bearing and nonbearing years had meaningful relation with fertilization as well. The average infection percentage of the fertilized trees in bearing year was 3.7% more than nonbearing year whereas this amount in non-fertilized trees was 9.8%. The results of this survey showed that accurate fertilization of olive trees had dramatic effect on OLS loss management and more attention to this issue is absolutely necessary.