U2Pt2Sn crystallizes in the tetragonal Zr3Al2-type structure (P42/mnm, Z = 4), where uranium atoms occupy two different sites. Our measurements of bulk properties have shown that in addition to antiferromagnetic order below TN = 15 K, there exists another magnetic-field-induced transition at lower temperature TN. The frequency dependence of TN and TN suggests two different sublattices of magnetic uranium ions in the compound. The first one, determined by essentially static uranium spins, which order antiferromagnetically below TN. The second uranium sublattice consists of rapidly fluctuating spins, which could in principle correspond to the anomaly at TN. To get information about evoluation of spin structure in magnetic fields, spin fluctuation and spin dynamics below TN and TN we propose to measure zero field (ZF) and longitudinal field (LF) mSR in magnetic fields up to 2.5 kOe.