Effects of biological carbon(bio-char)on sugar beet growth were studied by pot experiments simulating long residual herbicide residues in soil environment. The results showed that the safety threshold of sugar beet growth with clomazone residual was 0.12 mg·kg-1, and beyond this value, sugar beet growth was in inhibition with clomazone residues increased gradually;Early seedling growth under severe phyto-toxicity inhibition rate reached 100%when clomazone concentration was greater than 0.48 mg·kg-1;Seedlings subjected to injury sym-ptoms generally reduced to no phytotoxicity after put into a certain amount of bio-car in soil, the plant growth and root shoot ratio increased. Sugar beet root tuber yield and total sugar yield were influenced after applying carbon, sugar content increased 1.10%, which showed significant difference compared with CK. It explained that the bio-char could promote the growth of sugar beet. Applying biochar to soil could reduce the biological hazardous taken by clomazone residues within certain scope.