Green microalgae Pediastrum spp. from Chiang Mai Moat, Chiang Mai province, northern Thailand were isolated in Jaworski’s medium (JM) at 25 ºC under continuous light. Dominant species in this study were selected for optimal study of media, pH and temperature. Cell density was determined spectrophotometrically at a wavelength of 665 nm, cell counts by whole counts method and biomass productivity as dry weight. It was found that P. duplex, P. simplex and P. tetras grew best in JM followed by the growth in Bold’s Basal Medium (BBM) and Algal Medium (AM) media respectively. They grew better at pH 8.0 in JM and exhibited highest growth at room temperature. The protein content (36.45 ± 3.75 g/100 g) was highest in P. duplex and highest carbohydrate (43.86±1.75 g/100g) was found in P. tetras. Protein and carbohydrate were the major components in these algae which can be applied as food supplement in human and animal feed and pharmaceutical industries. Carbohydrate value was interesting as polysaccharide for sources of antioxidant. Pediastrum spp. have a large size which is easy for the cells to be harvested.