Recently, there has been an increasing interest in spherulites because of their excellent physicochemical properties and remarkable radial morphologies. However, their formation mechanisms remain largely unresolved and are often overlooked in industrial crystallization. In this work, it was demonstrated that the sodium percarbonate (SPC) spherical particle primarily results from the spherulitic growth effect rather than agglomeration effect. And then, in situ nucleation-controlled experiments in Petri dish were established to study the growth kinetics and morphologies of SPC spherulite. During the process, a critical growth rate was first discovered, which divides the spherulite formation into branching and nonbranching stage. A kinetic model was established to study the growth regime for SPC spherulite formation. Moreover, it is found that sodium hexametaphosphate (SHMP) is not necessary for SPC spherulite, but it can promote the branching of SPC which makes it possible to produce compact SPC spherulite product. On the basis of the experimental results, it is proposed that inducing branching and reducing the kinetic coefficient of the interface reaction are the sufficient conditions for spherulite product, which can be applied to other needle-like crystals to form spherulites.