This study was conducted at the Poultry Research Station in Abu Ghraib, Department of Agricultural Research, Ministry of Agriculture, the experimental field during three months (Three terms for a period of four weeks), from 10 th of December 2019 to the 10 th of January 2020. The study aimed to determine the effect of using different proportions of chlorella algae in layer hen ration and its effect on the hen's productive performance and numbers of lactobacilli bacteria in the intestine. The experiment included 400 laying hens (ISA Brown) of 54 week old which were fed according to the standard requirements mentioned in the guide for this breed (ISA Brown layer management guide). The hens raised using a 3 stage cages system with five hens in each cage. The birds were randomly distributed to five feeding treatments with four replications per treatment. The single replicate consists of 20 birds (80 birds per treatment). The treatments were as First treatment (T 1) without using chlorella algae (control) 'Second treatment (T 2) using 1% chlorella algae 'Third treatment (T 3) using 1.5% chlorella algae 'Fourth treatment (T 4) using 2% chlorella algae 'Fifth treatment (T 5) use of 2.5% chlorella algae The results indicated a significant improvement (P<0.05) in the egg production rate for T 2 , T 3 , T 4 treatments during the three trial periods (54-58, 58-62 and 62-66) a week, as well as the total period of the trial compared to the control treatment, and moral superiority (P<0.05) in the egg weight ratio for the T 5 treatment during periods (58-62 and 62-66) a week and the total period of the experiment compared to the control treatment. A significant increase (P <0.05) in the average egg mass for chlorella treatments (T 5 , T 4 , T 3 , T 2) during the periods (58-62 and 62-66) a week and the total period of the experiment compared with the control treatment T 1 and the results showed a significant improvement (P <0.05) in the rate of feed conversion in favor of coefficients for chlorella algae (T 5 , T 4 , T 3 , T 2) during the periods (58-62 and 62-66) a week and the total period of the trial compared with the control treatment T 1 .