Supercooling directional solidification (SDS) is put forward by combination of melt supercooling and conventional solidification by application of supercooling inheritance. On the self-designed SDS equipment, SDS of Cu-Ni alloy was achieved successfully. The results are as follows: (ⅰ) The primary arm spacing is about 30 m m, the growth of secondary arms are strongly suppressed. The primary arm spacing is nearly the same as LMC method (GL=25 K/mm, V=500 m m/s), the primary stems are straight, fine and completed, with an inclination angle of about 5.8o. (ⅱ) A semi-quantitative T-T model is brought forward to describe the dendrite growth rate V vs. undercooling D T. The prediction of T-T model agrees well with experimental results. The formation of fine equiaxed dendrites, transition region and dendrite region can be explained successfully by D T-V-x relation of T-T model.