The present invention relates to continuous dehydrogenating sodium oxalate producing process and apparatus with overheat steam jetting and mixing for fast heating. Overheat steam as heat carrier is used to heat fused sodium formate directly in a jetting mixer, so that sodium formate is heated quickly to pass over the temperature zone with incidental side reaction. After dehydrogenation in the self circulating dehydrogenating reactor, the product sodium oxalate is carried by airflow fast to the cooling and recovering tower for fast cooling without decomposition. The technological process may be used in continuous production, and has high sodium oxalate yield, high safety and capacity of obtaining sodium oxalate solution directly.