Abstract: As the business scale of the internet of things (IoT) platform continues to increase, it is very essential to monitor and evaluate the quality of service (QoS) for IoT platform, and to quickly locate faults to ensure the normal operation of the IoT platform. This paper proposes a QoS monitoring system and scheme based on probe technology. Through collecting, processing and analyzing platform business data, it realized the visual display and all-round monitoring of QoS for platform. Experimental results on OneNET IoT platform show that the system can gather and analyze various types of service data of OneNET, evaluate and display QoS through indicators such as time delay and satisfaction, give a useful tool for operation and maintenance personnel to find abnormalities accurately, and improve the efficiency of operation and maintenance.