Abstract: To predict the conditions of large rotating machinery, a gray prediction model was proposed, and an open and flexible prediction system based on virtual instrument (VI) was developed for easy adaptation to new users and application. This system was developed by using LabVIEW and VC++,and has been applied in industry. The results of practical verification on large pumps indicate that the technology presented is capable of predicting the date of a fault and reducing the times and cost of maintenance.