The saturated moist air with temperature T, pressure P and specific humidity q may be considered as an equivalent dry model air with temperature T* and pressure P under the condition of constant enthalpy. The features of the equivalent dry model air are described and the diagnostic analyses for the summer monsoon over Eastern Asia are examined. Results show that there are obvious baroclinicity features of equivalent temperature, i. e., wet baroclinicity, with a strong gradient belt of equivalent temperature for a time scale mean about 30 days in summer monsoon region and it is in accord with the confluence belt of the warmer air and colder air expressed by equivalent temperature; the mean updraft was observed at its warmer part of that region and downdraft at its colder part; the vertical shear of horizontal wind vector between 150 hPa and 850 hPa is related to the mass field expressed by mean equivalent temperature in that layer.These seem to indicate that the wet baroclinicity in summer monsoon region The saturated moist air with temperature T, pressure P and specific humidity q may be considered as an equivalent dry model air with temperature T * and pressure P under the condition of constant enthalpy. The features of the equivalent dry model air are described and the diagnostic Analyses for the summer monsoon over Eastern Asia are examined. Results show that there are obvious baroclinic features of the equivalent temperature, ie, wet baroclinicity, with a strong gradient belt of equivalent temperature for a time scale scale about about 30 days in summer monsoon region and it is in accord with the confluence belt of the warmer air and colder air expressed by the equivalent temperature; the mean updraft was observed at its warmer part of that region and downdraft at its colder part; the vertical shear of horizontal wind vector between 150 hPa and 850 hPa is related to the mass field expressed by mean equivalent temperature in that layer. These seem to indicate that the wet baroclinicity in sum mer monsoon region