One way to effectively use rice straw without causing environmental pollution is to produce biochar and reuse it to improve rice yield and soil properties. Using rice straw biochar has increased rice productivity and can reduce chemical fertilizers. Therefore, this study aimed to evaluate the effects of rice straw biochar application with reduced chemical fertilizer on the growth and yield of rice at Quang Phu commune, Quang Dien district, Thua Thien Hue province, Vietnam with four treatments of the co-application of rice straw biochar doses of 5, 7.5 and 10 t/ha and chemical fertilizers of 75, 50 and 25% of the recommended dose. Growth parameters, yield components, yield of rice, and soil property were investigated. The results showed that the rice straw biochar had a positive effect on the growth, yield of rice, and soil properties. The co-application of rice straw biochar of the level of 10 t/ha and chemical fertilizer of 25% of the recommended dose was optimal levels produced the highest growth and yield (63 t/ ha). The co-application of rice straw biochar and chemical fertilizers increased organic matter, improved both soil physical and chemical properties, and reduced chemical fertilizer use. As a result, the rice straw biochar may be recommended to farmers to apply for rice production.