This study aims to find optimum stock condition of microalga on strains preservation. Microalga included 1 Skeletonema costatum (SKE), 1 Thalassiosira weissflogii (CY), 1 Nannochloropsis oceanica (NJ), 2 Tetraselmis chui (TC1, LB232) and 5 Chaetoceros gracilis (CG1, CG2, CG3, CG4, CG5), the microalga strains came from different native place. The results showed that optimum temperature and photosynthetically active radiation of microalga stock condition are 25 ℃ and 100 umol/m2 /s for culturing NJ, TC1, SKE, CG1 and CG2; 20 ℃ and 100 umol/m2 /s for culturing LB232, CY; 15 ℃ and 50 umol/m2 /s for CG3; 20-30 ℃ and 50 umol/m2 /s for CG4; 30 ℃ and 50 or 100 umol/m2 /s for CG5 respectively. The optimum microalga stock mediums are CG2 in Walne, CG1, CG4 and CG5 in Walne plus simple formula for green algae, TC1 in f/2, SKE in f/2 plus simple formula for green algae. The optimum degrees of salinity is 25-30 psu for Chaetoceros gracilis (CG2, CG3, CG4). Microalgae culture experiments, pumping trace amounts of carbon dioxide or air in can promote the growth rate of the majority of strains of microalgae, and maintain PH value of the culture medium.