Using the conventional observation data, NCEP reanalysis data, two cases of spring torrential rains in Shandong Peninsula are studied. The results show that the rainfall caused by spring Huang Huai cyclone in Shandong Peninsula is concentrated in the northern part of the cyclone and mainly located in the northeast air stream. The northerly extent of rainfall areas are related with synoptic backward extent and the existence of the high pressure in Northeast China. When the synoptic system is obviously backward and the frontal slope is small, warm air stream along the front climbs north further and the rainfall moves northerly. If there is a high pressure in Northeast China, northeasterly wind at the southern side of the high invades the vortex at 850 hPa joined by the southeasterly wind. The asymptotic convergence in the northern part of the vortex generates the rainfall. Furthermore, the formation of cold northeasterly air stream is favorable for the climbing of warm air northward. In operation, it is necessary to analyze the spatial structure of the system and the impact of the surrounding temperature field comprehensively.