The biochemical components of two freshwater microalgae, Oocystis solitaria and Selenastrum sp., which were cultured in the media supplemented with different ferric citrate (0, 0.0039, 0.039 and 0.39 mg/L), were studied in this paper. The results indicated that O. solitaria in medium added with 0.039 mg/L ferric citrate had the highest protein content, carbohydrate content, chlorophyll a content and carotenoid content, while Selenastrum sp. in medium with 0.39 mg/L ferric citrate had the highest protein content, carbohydrate content, chlorophyll a content and carotenoid content. Both the microalgae in media with 0.39 mg/L ferric citrate had the highest total lipid contents, which were 13.7% and 22.78% for O. solitaria and Selenastrum sp. respectively, and increased 318% and 160% of that in media without ferric citrate supplementation. 18:3n3 and 18:2n6 were the dominant fatty acids in O. solitaria and Selenastrum sp. respectively. A higher ferric citrate concentration in medium induced higher level of saturated fatty acids in both the microalgae. It is therefore suggested that compared to O. solitaria, Selenastrum sp. has stronger tolerance with high ferric ion concentration and is more suitable for production of microalgae biodiesel.