Escherichia coli causes a wide variety of infections in poultry. Florfenicol is a broad-spectrum synthetic antibiotic which is effective against colibacillosis in poultry. This study was conducted to compare two commercial florfenicol ۱۰% in a broiler flock around Ghaem-Shahr city in Mazandaran province. There were three houses in the selected farm each with a capacity of about ۹۰۰۰ broiler chickens. Management and nutritional conditions and all health and vaccination programs were the same in all three houses. By observing the respiratory complications, signs and deaths caused by colibacillosis in the ۵th week in all three houses and after performing the antibiogram test, birds in houses ۱ and ۲ received the oral solution of Florfenidem ۱۰% (Delos Medica, Romania) and birds in house ۳ received the oral solution of Florfen ۱۰% (Rooyan Darou, Iran) from the age of ۳۳ days onward based on the dose recommended by the manufacturers in the drinking water for ۵ days. Before administering the antibiotic, sampling and bacteriological culture were done from the dead carcasses with colibacillosis lesions. After the isolation of Escherichia coli, antimicrobial sensitivity test was performed. A number of ۱۰۰ chicks from each house from ۷ -۴۹ days of age were weighed with a weekly interval. Food consumption and the FCR were calculated at the end of the production period in all houses. The percentage of various diseases and complications and the resulting deaths were recorded in all houses. The results of each of the aforementioned parameters in three houses were compared and analyzed with appropriate statistical methods. Due to the occurrence of coccidial enteritis, Bycox and Neomycin were used in all houses for treatment. Timely treatment of the herd against diseases caused good control of the disease. The herd performance after treatment was satisfactory. The problem of coccidiosis in the herd had a bad effect on the performance of the herd. At the end of the period (۴۹ days), the percentage of total mortalities was the lowest in house ۱ and the highest in house ۳. The average total mortalities in houses using Florfenidem was ۲۰.۹۷% and the total mortalities of house ۳ was ۲۵.۲۸%. Based on the results of this trial, it was found that the oral solution of Florfenidem ۱۰% (Delos Medica) and the oral solution of Florfen ۱۰% (Rooyan Darou) did not differ from each other and both can be used in poultry flocks against colibacillosis, if required.