A new adjustable magneto-optical isolator in near-infrared region is repotod. Based on the theoretical analysis an adjustable magnetic field system is designed for 45° Faraday rotator, getting a 1.0°-1.5° adjustable region under the condition of saturation, by which the characteristics of magneto-optical isolator are improved effectively that are influenced by the temperature characteristics of magneto-optical crystal, strong external magnetic firld, ageing effect of device and so on. The experimental results are obtained at 1.3 μm and at room temperature (T=25 ℃). Its insertion loss is less than 1.8 dB and isolation is over 29 dB.