Abstract: A VB-based real-time monitoring host computer system of temperature and humidity was studied and designed.Real-time monitoring of temperature and humidity data collected in the field could achieved，and for different crops，when environmental temperature and humidity parameters limit was exceeded，sound alarm was startup，so that an administrator intervened automatically or manual regulation.It would provide optimum temperature and humidity environment for growth of greenhouse crops，and degree of automation and production efficiency of greenhouse was improved.Design idea of software engineering was applied.Microsoft Visual Basic 6.0 was development environment.Microsoft Access was the back-end database.Using modular design method and technologies of object-oriented and database，functions such as real-time display of system data，information and data storage，historical data query，statistical analysis，print and abnormal alarm，were completed，and upper machine system monitoring tasks were realized.Overall design of the system and design of each functional module were described.Main function of system was explained.Operation interface and part of code of system were provided.Some measures for system and database security were also taken.