In order to meet the needs of simulated flight training and build virtual instrument with strong authenticity and support for multi-platform operation, the key technologies of virtual instrument system are discussed. Based on Visual Studio 2003 and GL Studio platform, on the basis of existing traditional instrument, and parameters of the button control system part, provide some addition logic algorithm for implementing the following functions. By setting the cache object makes the data transmission of master and manual operation and can run at the same time, improve the instrument human-computer interaction ability. A timer system suitable for virtual instrument is designed. On the basis of the timer, a button control response system is set up to recognize the button behavior freely and improve the flexibility of the using of buttons. Finally, a digital instrument is constructed based on the algorithm operates well, verified the algorithm and the above functions are basically realized, and the above key technologies are proved to be effective by operation results.