Abstract: An improved linear regression arithmetic of groundbased dualfrequency microwave radiometers to retrieve the atmosphere refractivity is put forward. It sets the dry item and wet item of the refractivity as the input of surface weather parameter. So it can reflect the relativity between the atmosphere refractivity and surface weather parameter better. Physical concept of the format is also clear. The simulation of historical data of Yichun, Harbin, Jinzhou, Taiyuan, Qingdao, Guangzhou and Sanya area has proved the validity of the arithmetic. The results show that the retrieving precision of the improved linear regression arithmetic is generally increased below 5 km especially for the atmosphere near ground.