Abstract: To explore nutrition physiologcial mechanism in rice seedlings under arsenic stress, a hydroponics experiment was conducted on nutrition physiological and molecular response of “Shanyou63” rice seedlings under stress of different forms of inorganic arsenic. Morphological indexes of root length, shoot height and dry weight, and NPK content in plants were analyzed after As(Ⅲ) and As(Ⅴ) treatments. More importantly, four rice genes correlating with key enzymes regulating NPK absorption were determinted by Real-time Fluorescent Quantitative PCR to evaluate expression changes under stress of different forms of inorganic arsenic. The results show that root length, plant height, and dry weight of rice seedlings significantly drop after treatment of arsenic. As(Ⅲ) is more toxic than As(Ⅴ). While phosphorus and potassium accumulation is suppressed mainly by As(Ⅲ), nitrogen on the other hand is suppressed mainly by As(Ⅴ). A less regulated gene expression in relation to nitrogen, phosphorus and potassium absorption is observed after arsenic treatment. As(Ⅲ) has a greater suppression on phosphate and potassium transporter protein expression than As(Ⅴ). As(Ⅴ) on the other hand has a greater suppression on nitrate and ammonium transporter protein expression than As(Ⅲ). This implies that As(Ⅲ) and As(Ⅴ) differently influence nutrition physiological mechanism of rice seedlings.