Drilling fluid real-time on-line monitoring system is a real-time monitoring system for the performance parameters of drilling fluid in the process of drilling. A device that can realize real-time measurement of drilling fluid temperature, density and rheological properties. The system can obtain more accurate, more comprehensive and more timely drilling fluid performance data every 5 minutes, so that the operator can quickly deal with the complex downhole conditions, the operation of instruments and the operation of the whole control and monitoring system. In the process of drilling, the density and rheological properties of drilling fluid can be monitored in real time, which can provide effective data support for decision-making in the process of drilling, reduce operation risk and improve drilling efficiency, so as to achieve the best drilling effect. The connecting device of the monitoring system adopts standard size pipeline, which can be connected with most drill floors.