The compositions of platinum-group elements (PGE) and the assemblages of platinum-group minerals (PGMs) in mafic-ultramafic rocks and related magmatic deposits are the results of diverse processes, such as mantle partial melting, fractional crystallization of mafic-ultramafic magmas, and the segregation and migration of sulfide melts. Therefore, PGE and PGM can be used to reveal the processes of magmatic differentiation and ore formation. Here, we introduce some case studies showing that PGE partitioning pattern and PGM assemblages can indicate the formation and evolution of ophiolitic peridotite, podiform chromitite and magmatic sulfide deposit. Firstly, in the harzburgites of K?z?lda? ophiolite from Türkiye, the total content of PGE ranges from 18.15 to 39.65 ×10-9, with narrow ranges of Os, Ir and Ru, variable ranges of Pd and Pd, and high Pd/Ir and Pt/Ir ratios. All harzburgite samples have consistent and relatively flat PGE patterns when normalized to the primitive mantle. Base on PGE and trace element compositions and quantitative models, we concluded that the harzburgites of K?z?lda? ophiolite are the products of 20% partial melting of primary mantle and melt-rock interaction. Secondly, the PGM assemblages in different types of chromitite from K?z?lda? ophiolite are different. In all chromitite samples, primary laurite and Os-Ir alloy are typically enclosed within chromite, suggesting the crystallization of chromite at temperature of 1100–1200℃ and log?S2 values of -2 to -1. However, in nodular ores, Os-Ru nanoparticle + OsRu3 nanoalloy + awaruite (FeNi3) + trevorite (Fe2NiO4) are located in the intergranular space of chromite, indicating that the nodular chromitite underwent weak serpentinization and had low water/rock ratios (<~1), fS2 and fO2. On the other hand, in banded and massive chromitite, Os-rich laurite + Os-Ir(Ru) alloy/oxide + pentlandite + millerite (NiS) are located in the intergranular space of chromite, suggesting high water/rock ratios and high fS2 and fO2 during serpentinization. Thirdly, in the J-M reef of the Stillwater Complex, Montana, USA, we discovered a new mineral, Wangyanite. Wangyanite is a Pd end-member mineral of the pentlandite group, which has 9.64-10.59% Pd. Based on the textural features and previous experimental Pd-Fe-Ni-S phase system, wangyanite could form by peritectic reaction between braggite, pentlandite and sulfide liquid, rather than exsolved from monosulfide solid solution (MSS) and intermediate solid solution (ISS). To sum up, the studies of PGE compositions and PGM assemblages can provide new information on the magmatic deposit formation process and mechanism.