Demonstration experiment is an important link in science and engineering teaching. This paper discusses the application of virtual instrument technology to demonstration experiment teaching of science and engineering. The teaching system of demonstration experiment is composed of virtual instrument, experimental device or circuit, multimedia computer, etc. It can demonstrate many experiments such as the physical experiment, electrics experiment, electronic technology experiment, automatic control principle experiment, etc. Using the technologies of virtual instrument and multimedia to demonstration experiment teaching of science and engineering realizes the computerization and digitization of demonstration experiment teaching. It not only improves the visibility and effect of demonstration experiment teaching but also enhances the efficiency and level of demonstration experiment. It has an inestimable effect on the modernization of the experiment teaching.