Solidtosolid phase transformation plays an important role in controlling microstructures in metallic materials. Specific orientation relationship (OR) and interfacial orientation (IO) are formed due to the reduction of the nucleation barrier via reducing the interfacial energy during phase transformation. The formation of such specific ORs and IOs is called the preference in transformation crystallography. In addition to phase transformation thermodynamics and kinetics, phase transformation crystallography is also indispensable for understanding the formation of various microstructures. Interfaces and their structures are the keys to understand the transformation crystallography. Specifically, interfacial matching is a common concept in geometric methods applied to study the crystallographic features generated from phase transformation. In this review, the method based on good matching sites (GMSs) in the interface is shown to qualitatively understand the transformation crystallography. The quantitative tool to describe the distribution of GMSs, ie. Olattice theory, is reviewed thereafter. Geometrical methods based on Olattice theory are further explored. Although the inputs for geometrical method are simple, usually needs lattice parameters of two phases during phase transformation, its outputs are rich in crystallographic features. Finally, a free software for transformation crystallography has been developed recently by us, PTCLab, is applied to understand the precipitation of austenite in duplex stainless steel. In principle, the concept reviewed in this paper could be also applicable to analyzing grain boundaries.