Virtual inst rument technology is a new developing softw are application technology, it opens up the new situation of the instrument field. The concept of virtual instrument and the function of Lab Windows/ CVI are mainly introduced. A set of virtual instrument with mult-i parameter for water quality monitored by using Lab Windows/ CV I is advanced,and the hardw are constitution and software design of the virtual inst rument are given. Furthermore an application example for monitoring water quality with virtual instrument is presented. The main characteristics of the virtual instrument are its flexibility, high ratio between performance and cost, powerful functions and good extensibility,and show that using the virtual instrument is an effective way which monitors water quality.The development of virtual inst rument technology in w ater industry is also prospected at the end.