Abstract: Investigation of the optimal harvest time to obtain high feeding quality rice (Oryza sativa) straw would be useful to increase the utility of rice straw as roughage. Four rice varieties Liangyoupeijiu (late maturing medium indica), Wuyujing No.3 (late maturing medium japonica), Nanjing44 (early maturing late japonica), and Nanjing46 (medium maturing late japonica) were used. The effects of five harvest times: 6 days before the theoretical whole growth period (TWP), 3 days before TWP, TWP, 3 days after TWP, 6 days after TWP, on the grain and straw yield, the rice straw feeding quality related traits such as nonstructural carbohydrates (NSC), crude protein (CP), acid detergent fiber (ADF) contents and in vitro dry matter digestibility (IVDMD) and the fermentation quality of straw silage were investigated. The grain yields increased with a delay of harvest time; NSC content in the rice straw of Liangyoupeijiu 6 days before TWP, Nanjing44 3 days before TWP, Wuyujing No.3 3 days after TWP and Nanjing46 6 days after TWP were the highest of the 5 harvest times. CP content in rice straw decreased with a delay of harvest time. The change trends of straw yielding, IVDMD and the fermentation quality were consistent with that of NSC content. In order to get high quality rice straw feed, but not to significantly decrease grain yields, the optimal harvest time of Liangyoupeijiu was 6 days before TWP, Nanjing44 and Wuyujing No.3 were 3 days after TWP, and Nanjing46 was 6 days after TWP.