The key of the distributed monitoring network construction is to select different types of sensors according to the monitoring parameters, and to select the matched data acquisition module referring to the output of signal sensor. On the basis of the construction of distributed monitoring network, the computer serial ports RS-232 and RS-485 are used to realize serial communication, realizing multipoint and real-time monitoring. This paper discusses how to realize the serial communication based on Visual Basic, discusses the method of building distributed monitoring network based on Nudam I-7000 module, and introduces the construction and programing of a small monitoring network using temperature and humidity sensor and distributed module.