Some laser experimental parameters in infrared nonlinear optical crystal GaSe were calculated, including the illustration of phase matching angle, the varying of effective nonlinear coefficient, allowing angle, walk-off angle and Sellmeier curve for type I and II phase-matching. All the results were calculated in the optical parametric oscillation (OPO) and second harmonic generation (SHG). Also, the results were analysed so that they can provide useful theoretical references for optical design of infrared tunable and new wavelength laser devices.