Abstract: The present application relates to a CoAP-based OPC UA message transmission method, comprising: packaging and encoding data by using an OPC UA information model; packaging an entire OPC UA data message into a load part of a CoAP message; then, on the basis of a UA-CoAP server, querying whether a CoAP-to-HTTP proxy server is present in a network; if present, transmitting a UA-CoAP data message to the CoAP-to-HTTP proxy server; converting the received data message into HTTP; and transmitting the data message to an OPC UA client. The present application solves the problem wherein data of a limited-resource industrial field device cannot be uniformly described and cannot be uniformly accessed, while the requirement of the industrial field device accessing a web service is satisfied.