Abstract: In order to grasp the effect of red sun shading net on the growth and fruit quality of tomatoes, on the basis of plastic greenhouse, the large-plot field experiments with the red sun shading net coverage and white drip-free film coverage (the control group) were conducted to analyze the spectral components, tomato growth, yield and quality under different treatments. The results showed that the coverage of red sun shading net reduced the photosynthetic active radiation, increased the ratio of red light to blue light and the ratio of red light to far-red light. After the red sun shading net was covered, the content of soluble solid, the ratio of sugar to acid, the brightness and redness of peel increased by 10.2%, 17.3%, 28.9% and 42.7%, respectively, compared with the control group, while the yield and output value of tomato increased by 15.4% and 17.9%, respectively. Compared with the control group, the red sun shading net coverage had no significant effect on the fruit shape index of tomato, vitamin C content, soluble sugar content, titratable acid content, and the contents of nitrogen, phosphorus and potassium. The results showed that the coverage of red sun shading net may increase the proportion of red light to blue light by reducing the blue light transmittance, and promote the improvement of tomato yield, fruit flavor quality and appearance quality.