Abstract: Drilling automation is an inevitable trend in the development of petroleum industry, and the automatic measurement of the drilling fluid properties is now finding more and more application in field operation instead of just being a laboratory tool. The Research Institute of Drilling Technology of Shengli Oilfield (Sinopec) has recently independently developed an instrument that is used to online measure the properties of drilling fluids. The instrument can be used to measure the properties of drilling fluids in a real-time, continuous and automatic manner, and the measuring data can be transmitted to remote area. Drilling fluid properties measured with variable diameter rheology test method, dual-tube serial vibrating tube and ion-selective electrode method are integrated by a data acquisition system. The software used with the measuring instrument has nine pages displaying intuitively the acquired data in graphical form. This instrument has been tried in the drilling of many wells in the Shengli Oilfield and three HTHP deep wells by CNOOC, the highest density of mud used was 2.30 g/cm³. Properties measured with the instrument are basically consistent with the manually measured data, with test errors being in the designed ranges. Using this instrument, drilling efficiency is enhanced and downhole safety is ensured. The development of this instrument is required by the national oil and gas safety strategy, and is of great significance to the acceleration of drilling automation, drilling informatization and intelligent upgrading and transformation of drilling operation.