Abstract: Using conventional observation data from 2000 to 2009 and ECMWF global objective analysis of initial field with resolution 2.5°×2.5°, the sustained rainstorm (SR) processes from May to August in northeast Guangxi have been analyzed and its prediction skill has been evaluated, with statistical classification method, synoptic and climatological analysis and ingredients based method, etc. The results indicate that SRs in northeast Guangxi mainly occur from late May to late June, whose duration is from 2 to 4 days, and most of them last for 2 days. The SRs in this area can be classified into four primary categories and six sub-categories according to the configuration of weather systems.An objective system for automatic forecasting sustained rainstorm established by combining information on synoptic pattern, numerical forecast products and physical quantity ingredients can provide objective references for SR forecast in northeast Guangxi.