Effect of temperature, photoperiod and irradianceonthe amount of agar in Gracilariasalicorniawas evaluatedunder laboratory condition during 42 days. The alga .Gsalicornia was sampled from coasts of Gheshm Island in Hormozgan province in September 2009.The algae were raised in aquariums (40×30×60 cm) with 20 litercapacity, in 3 replicates. Light required intensity to grow was 4700 lux and temperature was 25^oC. The algae were cultured intemperatures 20,25 and 30, photoperiod (12:12, 14:10 and 16:8.light:dark cycles). The algae were harvested once a week and weighted. At 6 weeks after experiments, the algae were collected, dried and weighed. َAgar content were extracted usingCarmanamethod. The highest biomass of G.salicornia was calculated at 20,12:12 light: dark cycle and 4700 lux. Maximum level of agar was observed in temperature25^oC equal to 45 percent. As the results, G.corticatacould be one of commercial algae in the world.