Abstract: Based on the on-line monitoring system of aluminium alloy spot welding the database was constructed.The database connected with the on-line monitoring system based on LabVIEW to record and slave the real-time quality information of nuggets.The database also supports nugget information querying and managing and worker information querying and managing.This functions are very suitable for aerial manufacture and the factory practicality.The X-chart is used to estimate the critical value of the nugget quality by analyzing the database information,and the critical value is feed back to the on-line monitoring system.The results of experiments indicate that this on-line monitoring system has achieved high precision in the nugget quality estimation,and it has been used in the aerial products spot welding now.