The selecting experiment on ut ilizing starch wastewater by f ive Candida tropicalis strains and their transforming of selenium were studied. The result s showed that the strain of CY-173 produced more protein and protein-form selenium than the others . The temperature tolerance test proved that the bacteria were able to grow upto 33- 45 e . The growth rate slowed down when temperature were above 40 e and the growth was inhibited at 45 e . An experiment concerning the ef fects of pH and temperatures on their growth rate and the amount of protein produced was also carried out in a standard 6-liter tun. The dif ference of growth rates of the strains was not significant at pH 3- 5 , and they could grow normally at 33- 40 e . The amounts of protein and protein-form selenium produced by the strains reached the highest level at 37 e .Feed with the seleniumrich yeast was used in the culture of Penaeus chinensis . The results showed that the three groups fed with the selenium-rich yeast ( containing 10% , 20%, 30% selenium yeast ) had better effect s than the control group , and the group with 10% of the yeast ( containing 0. 6 @ 10 - 6 selenium ) had the lowest feed rat io, 2. 56, reducing 13. 3% compared with the control group.