This work studies the acicular ferrite (AF) nucleation and growth from a classical defect, i.e. non-metallic inclusion surface. The heterogeneous AF-nucleation probability on NMI is predicted by a mathematical model following the classical nucleation theory. The calculation results are in consistent with the exper-imental data. The current model includes the exact form of the activation energy and Zeldovich factor for heterogeneous nucleation on pre-existing spherical surface. It generates an interaction map that for the first time quantitatively describes the superposition influences of the interfacial energies and NMI-size on the AF-nucleation potency. In the AF-growth aspect, we systematically reveal the single AF-plate evo-lution behavior through the synergy between the experimental observations and multiphase-field simu-lations. It is found that the AF-tip morphology is impacted by the misorientation angle between the favorable growth direction and normal vector. It also influences the AF-lengthening and widening kinet-ics. Additionally, the anisotropic stress field induced by the AF-NMI interface plays a significant role in controlling the complex curvature of the AF-plate. The current study opens new perspectives for under-standing the AF-precipitation mechanisms.