Abstract: The jet grouting mixing stiffening pile is a new and initiative supporting technology in foundation pits. Engineering practices show that the unique structural design of stiffening piles enhances the pullout resistance and soil strength. The foundation deformation of stiffening piles is better than that of bolting and nailing in soft soil. The load-deformation laws of stiffening pile are illustrated by static load tests. A method to quantitatively assess the pile side soil reinforcement of stiffening piles is derived. It is proposed that the rheological stress and concentration stress are the key factors to apply the stiffening piles in soft foundation pits. The reinforcement and support stiffness method is put for ward to guide the design and construction.