The effects of row space and irrigation on 100-seed weight water uptake, leaching loss, soymilk, and okara yield of soybean were investigated. Row space affected leaching loss, whereas irrigation significantly altered 100-seed weight, water uptake, volume change, leaching loss, and the soymilk yield of soybeans. Irrigation on the third day resulted in desirable hydration properties. The soymilk yield significantly correlated (p < 0.01 or 0.05) to the hydration properties, e.g., 100-seed weight, water uptake, volume change, and leaching loss. A predictive regression model (R = 0.860) has been proposed for the soymilk yield.