[Background] Chlorella sp. contains 20 amino acids needed for animal growth and rich in protein, polysaccharides, unsaturated fatty acids, carotenoids, astaxanthin and various vitamins. It can be used as high-quality natural bait for fish, shrimp and shellfish. [Objective] Chlorella TX was isolated from cultured environment. The method of mutagenesis was used to breed high biomass and protein content mutants in order to obtain excellent algae resources for aquaculture natural bait production. [Methods] Chlorella TX, a relatively fast-growing and high protein content algae, was screened from the aquaculture environment as the starting strain. 18S rRNA gene sequence analysis was employed to identify strain Chlorella TX, and then ultraviolet mutagenesis, ethyl methane sulfonate (EMS), compound mutagenesis, 96-well plate high-throughput screening and progressive repeated screening were used to breed high biomass and protein content mutants. [Results] TX was identified as Chlorella sorokiniana by 18S rRNA gene sequence analysis. Eight mutants with genetic stability and growing fast were screened out from 540 mutants after progressive repeated screening. The total protein, soluble protein content and dry weight content of mutant H10 were 64.2%, 0.44 g/L and 0.72 g/L respectively, which were 3.4%, 15.8% and 26.2% higher than original algae strain TX. [Conclusion] The advantageous characteristics of H10 with high protein and growing fast can be used for natural bait production.