NaY(WO4)2: Sm3+/Nd3+ microstructures were designed as the photothermal conversion materials for potential use of PTT. NaYF4: Yb3+/Er3+ phosphor was used as thermal probe to study on light to heat conversion process of the microstructures. Under co-excitation of 980 nm and 808 nm, the photothermal conversion induce effect on the microstructures was studied. The thermal effect was dependent on both the laser excitation current and Sm3+ concentration.