With reference to the 27 low visibility weather processes in Dongying from 2016 to 2017,thisresearch calculates the temperature difference of inversion layer,the thickness of inversion layer,andlow-level relative humidity at 10-min intervals by using the secondary data of MP-3000A ground-basedmicrowave radiometer. Combing the changes of air quality and visibility,the 27 processes are classifiedand studied according to three kinds of weather:fog and haze,fog,and precipitation. The temperatureand humidity measurements of microwave radiometer are of indicative meaning and can be an index of reference for low visibility weather. The results are as follows. (1)The low visibility weather caused bothby fog and haze appears in winter half year. Usually,the higher the PM2. 5 concentration,the lower thevisibility. The correlation coefficient between the temperature difference of inversion layer and visibility is-0. 39 and that between the thickness of inversion layer and visibility is -0. 45. The temperaturedifference increase of inversion layer indicates the decrease of visibility,while the thickness decrease ofinversion layer indicates the increase of visibility. Affected by fog,the visibility is usually less than 2 kmwhen the low-level relative humidity is higher than 90%;affected by haze,the visibility can maintainbelow 5 km even as the low-level relative humidity is lower than 80%. (2)The low visibility weathercaused by fog mostly occurs in winter half year,which has nothing to do with PM2. 5 concentration. Thecorrelation coefficient between the temperature difference of inversion layer and visibility is -0. 54 andthat between the thickness of inversion layer and visibility is -0. 45. In the formation or destruction stageof inversion layer,the temperature difference of inversion layer varies greatly and has a stronger indicationfor visibility,while the thickness of inversion layer is maintained between 300 m and 400 m and the rangeof variation is relatively small. When the low-level relative humidity is above 90%,the visibility is usuallyless than 5 km,whereas the visibility increases to be more than 5 km when the high-humidity layerdisappears. (3)The low visibility weather caused by precipitation appears in summer and it is mostlyaccompanied by short-time heavy precipitation. The temperature difference of inversion layer can reachover 8 ℃ and the thickness of inversion layer can reach 500 m during the period of heavy precipitation;the inversion disappears and the visibility increases after the heavy precipitation.