Can you use interior stain on outside deck?

CAN you? Yes, however you shouldn't unless it is well shielded from the sun's UV rays otherwise, it will quickly fade. Also, most interior stain has no mildewcides added so you'd need to apply an exterior clear over the top to slow mildew growth.

不可以将室内家具油或室内木器漆用于室外甲板。室内家具油和木器漆通常不具有抗紫外线、抗水性等特性，无法在室外环境中提供足够的保护和耐久性。室外甲板应使用专门设计用于室外环境的甲板保养油或甲板漆，这些产品能够更好地抵御阳光、风雨和温度变化，保护甲板免受损坏。