Abstract: Traditional dairy farming is based on the experience of farmers,the breeding process is time-consuming,labor-intensive and high breeding cost, mechatronics equipment research and development is an important part of improving the large-scale breeding of dairy cattle. This paper designed a set of environmental monitoring system based on programmable logic controller（PLC）,combined with PLC control and Internet of Things technology,to realize PLC configuration touch screen and IoT platform communication,the system can display the current environmental parameters in real time,automatically adjust the barn lights and fans and other equipment according to the change of environmental parameters,remotely send fault alarm information,etc.,reduce the burden of farms （households）,automatically improve the environment of large-scale farm barns and increase milk production and quality of dairy cows. After the system design is completed,it is applied to dairy farms,and the system is reliable and stable during use,and the interface is convenient to operate,which has good promotion and application value.

Key words: lactating cattle breeding, programmable logic controller（PLC）, configuration technology, Internet of Things