A continuous-wave (CW) single-frequency 1.5 μm laser source is obtained by a singly resonant optical parametric oscillator (SRO) based on periodically poled lithium niobate. The SRO is pumped by a CW single-frequency NdYVO4 laser at 1.06 μm with the pump threshold of 2.5 W. 3.2 W of CW single-frequency signal laser at 1.5 μm is achieved at pump power of 8 W with the optical conversion efficient of 40%. When the SRO is actively locked to the centre frequency of a Fabry-Perot cavity, the power stability is better than ±0.5% in 15 minutes and frequency stability is better than 3 MHz in 1 minute. The center wavelength of the laser system is in the wave band of quantum states transmission, so this kind of system can be employed for researches of practical quantum information processing.