Total phenolic content and total flavonoid content were evaluated among four species of alga: one brown algae (Cystoseira compressa), two green algae (Ulva lactuca and Enteromorpha intestinalis) and one red algae (Jania rubens). The seaweeds were collected from submerged rocks between 0 and 50 cm of depth during the month of March 2022 at Kouali – Tipaza in Algeria. The results obtained showed that Decoction method offers better value than maceration for the four algae species. Brown seaweed Cystoseira compressa has the highest polyphenol content, with 1,1057 ±0,0192 mg GAE/g and 0.332 ± 0.0074 mg GAE/g respectively for decoction and maceration. The same species offered 0.211 ± 0.0016 mg QAE/g of flavonoids which is the higher value. Cystoseira compressa represents a good source of phytochemicals for use as food and feed supplement.