In order to obtain the relationship between the position of the transmission peak of the photonic crystal defect and the refractive index (concentration) of the solution，a one-dimensional photonic crystal sensor model of defect layer constructed by sodium chloride solution is proposed. The relationship between defect peak wavelength and concentration of sodium chloride solution is calculated and analyzed by transfer matrix method. The results show that the wavelength of defect peak is proportional to the refractive index of solution and the concentration of sodium chloride. The sensitivity of solution concentration measured by the sensor model is 0.57 nm/%. The one-dimensional defect photonic crystal sensor model proposed in this paper has the advantages of high sensitivity, low temperature influence and real-time detection, which provides a theoretical reference for the design of practical photonic crystal sensors.