A monolithic single-frequency non-planar ring oscillator (NPRO) laser is studied. Continuous-wave (CW) output power of 1.01 W with 1.83 W pump power is achieved. The slope efficiency is about 60%. The laser linewidth is measured by beat frequency measurement method with another narrow linewidth single frequency laser, and the linewidth is less than 2 kHz. Besides, the suppression technique of intensity noise and frequency tuning characteristics are studied for the laser. The relaxation oscillation peak noise is suppressed by 30 dB through feedback control of pump laser diode driver current. The laser frequency can be tuned slowly by temperature tuning and quickly by piezoelectric transducer (PZT) loaded on the laser crystal. The laser frequency can change 15 GHz when the crystal temperature changes 10 ℃. Meanwhile, the laser frequency PZT tuning range exceeds ±200 MHz, and the response time is 45 μs when the frequency is tuned over 200 MHz.