To solve the problems of low early strength and poor water stability of stabilized red clay, the functional components including expansion component, early strength component, thin electrical double layer structure component, waterproof component are used to improve the early strength of stabilized soil by sulphoaluminate cement. Through the single doping tests, aluminum stearate, triethanolamine, Fe(NO3)3 and gypsum are selected as the functional components of soil stabilizer., The optimal formula of functional components is further determined by orthogonal test. The unconfined compressive strength of stabilized soil can reach 8.60 MPa after curing 7 days using the optimal formula. By using XRD and SEM, the variations of mineral composition and microstructure of the stabilized soil are analyzed before and after adding functional components. The test results show that functional components used in moderation can contribute to the formation of insoluble mineral crystals with high strength and expansibility, so as to improve the early strength of stabilized soil. However, if the amount of functional components is too high, the early strength of stabilized soil decreases due to the altered connection way of stabilized soil induced by the excessive expansion of mineral crystal and the hindrance of hydrophobic membrane.