Rare-earth doped yttrium orthosilicate (Y2SiO5) crystals have many important applications due to their unique optical and luminescence properties. However, the indispensable high temperature treatment and long period reaction tend to greatly reduce the preparation efficiency. Here, the plasmonic photothermal effect of Au nanoparticles has been properly applied to realize in situ transformation from a composite structure NaYF4:Eu3+@SiO2@Au into a single monoclinic X1-type Y2SiO5:Eu3+-Au particle. It is worth mentioning that the X1-type Y2SiO5-Au particle can be well obtained within about 10 seconds when the thickness of the SiO2 shell is about 15 nm, which is unattainable with conventional approaches. Moreover, the particle turns out to possess good crystallinity, controllable morphology, and significantly improved luminescence performance. This study not only provides a brand-new path for the preparation of yttrium silicate crystals but also further extends the application of surface plasmons in the field of catalytic luminescent materials.