The reason of misrun and cold - lap formation in thin - walled aluminum casting is analyzed . increasing gas exhaust capacity in mould and filling velocity and controlling melt temperature are favorable methods for better effect 对薄壁铸铝件浇不足及冷隔的形成原因进行了分析,提出了增大铸型排气性、提高充型速度、控制出炉温度的解决措施,效果良好。