Monodisperse Sr 2 YF 7 nanocrystals with the size of sub-10nm were synthesized via a solvothermal method by using oleate as a capping ligand. X-ray diffraction and transmission electron microscopy assays reveal that the as-synthesized Sr 2 YF 7 nanocrystals are face-centered cubic structure with the cell parameter a=5.704Å. Intense upconversion luminescence can be observed in Er 3+ /Yb 3+ and Tm 3+ /Yb 3+ codoped Sr 2 YF 7 nanocrystals under the excitation of a 980nm laser and near-white-color emission can be obtained in Er 3+ /Tm 3+ /Yb 3+ tri-doped Sr 2 YF 7 nanocrystals. Energy transfer (ET) from Yb 3+ to Er 3+ and Tm 3+ is mainly responsible to pump Er 3+ and Tm 3+ from the ground state to higher states. In Er 3+ /Tm 3+ /Yb 3+ tri-doped Sr 2 YF 7 nanocrystals, ET from Tm 3+ to Er 3+ leads average three-photon process, which renders the 523nm emission.