Although sulfur is an indispensable element for plants, its availability to plants in the presence of biochar is unclear. The effects of dairy manure biochar at the rate of 0, 0.5, 1, 2, and 5% on plant physiological characteristics, soil properties and sulfur phytoavailability in corn (Zea mays L.)-Calcids soil system were investigated using pot experiments with sulfate amendment at low, moderate and high level (0, 50 and 100 mg S kg^-1 soil). It was found that the plant height, fresh and dry weight, and chlorophyll content were significantly improved with the biochar addition rate increasing from 0 to 2% while largely decreased with the rate increasing from 2% to 5%. The moderate level of sulfate amendment favored the corn biomass and chlorophyll content. The pH values of soil were significantly increased with increasing biochar addition rate, reaching about 8.50 at the rate of 5%. The catalase, urease and sucrase activity in soil increased significantly with the biochar addition from 0 to 2% but largely decreased with the rate increasing from 2% to 5%. Too high pH values due to 5% biochar addition resulted in the inhibitory effects on plant growth and microorganism activity in soil. Biochar addition at low rates (<2%) and sulfate amendment at high level improved sulfur content in leaves and roots. The decreases of inorganic sulfur and total sulfur contents in soil with biochar addition rates significantly responded to the accumulation of sulfur in leaves and roots. The results show that co-application of biochar and sulfate with proper amount could improve the growth and sulfur phytoavailability of plant in calcareous soil.