A micro-TEHL finite line contact model for a helical gear pair is developed by considering sinusoidal waviness on tooth surfaces. Effects of working conditions, the amplitude, and the wavelength of the waviness roughness on the lubrication performance are studied. Results show that surface roughness has a significant influence on the pressure, the temperature, and so forth. The pressure within the nominal contact zone for a rough-surface case fluctuates around the smooth-surface solution. For the working conditions studied, at local area within the contact zone, the maximum pressure may be 50% higher than the smooth-surface result. The film contraction at the outlet zone becomes more remarkable. The film temperature also fluctuates regularly. As the amplitude of the roughness increases, the local pressure within the nominal contact zone increases while the minimum film thickness decreases. As the wavelength of the roughness decreases, the local pressure and the temperature within the nominal contact zone increase while the film thickness decreases. Effect of wavelength on the lubrication performance is more evident along the rolling speed direction than along the contact line direction.