Abstract: Based on the application of the low-frequency synoptic map (LFSM) for extended-range forecast of summer strong precipitation process in Shanghai for five years (2008—2012), this paper further explores the technical rules, technical points and technical methods of LFSM. The main contents include how to calculate and draw LFSM, the technical principles for the key regions' division of LFSM, the technical rules for analysis of the low-frequency weather systems and the foundation of the prediction model. Finally, with an instance of one strong precipitation process, the usage and weather principles are discussed for reference of the related weather operational departments during the spread of LFSM.