The objective of this study was to assess the effects of parity and lactation stage on the content and conversion rate of DHA in milk from dairy cows fed ruminally protected algae powder. A total of 800 cows were blocked by parity and divided into eight groups (n = 100, three groups of primiparous cows and five groups of multiparous cows) in a six-month experimental period. The lactation period was divided into three stages: 16 – 100 d, 101 – 200 d, and 201–305 d. All cows were fed 100 g of DHA-rich algae powder twice a day, with the DHA content > 13%. Milk samples were collected monthly, and daily milk yield and dry matter intake were recorded. Using infrared spectroscopy, we determined the content of protein, fat, lactose, and total solids in milk and calculated the DHA conversion rate. The results showed that parity and lactation stage had no significant effects on milk composition. However, milk yield and dry matter intake were higher in multiparous cows than in primiparous cows. The DHA content and conversion rate in milk were not significantly different between parity groups but were positively correlated with lactation stage and negatively correlated with milk fat content.