Abstract: Salt content is one of the most important indexes to evaluate the quality of salted duck eggs. The variety, source, size, and freshness of duck eggs can significantly affect the salting rate of duck eggs. Rapid salting technology (such as high-pressure pulsation) can promote the efficiency of osmotic dehydration. The difference in the raw materials can also be magnified to result in the uneven salt content of products. Therefore, it is crucial to precisely measure the salt content for the quality consistency of salted duck eggs. Rapid non-destructive testing of poultry eggs can include machine vision, spectral, and acoustic technology at present. Among them, near-infrared spectroscopy has been employed to measure the salt content of salted eggs. But its equipment cost is higher than the others. By contrast, machine vision is normally used to differentiate between deteriorated and high-quality eggs, due to its versatility, affordability, and large-scale detection. In this study, the acquisition device of the image was proposed to accurately detect the salt content of salted duck eggs using an industrial camera and transmission light source. There was a notable improvement in the light transmittance of salted duck eggs, as the salting time increased. Additionally, the visual field area with the yolk was gradually diminished in the transmission image. The color was lightened gradually with the regular changes until it nearly disappeared. There was a gradual increase in the average egg white, egg yolk, whole egg salt content, and egg yolk index, as the salting time increased. However, there was a significant variation in the salt content and yolk index of salted duck eggs under the same salting time. The eggshell and eggshell membrane served as the primary channels and barriers for the material exchange between the duck egg and the external salt solution. The high-pressure pulsation greatly contributed to the differences in the eggshell and eggshell membrane among individual duck eggs, further impacting the osmotic dehydration rate. Therefore, the salt content of salted duck eggs was required under conditions of high-pressure pulsating salting. The prediction model was established for the salt content and yolk index of egg white, yolk, and whole egg. The overall image features and long-axis cross-section light intensity were extracted using multiple linear regression and support vector machine. Results indicated that the overall image features were used to perform better on the prediction of egg white, yolk, and whole egg salt content. While the features of long-axis cross-section light intensity were more effective for the prediction of yolk index. Notably, the optimal combination was achieved in the support vector machine with the overall image features. The salt content of egg yolk was accurately detected in the test set with the R_p, RMSEp, and RPD of 0.846 0, 0.341 6, and 1.898, respectively. Furthermore, the optimal detection of egg yolk index was obtained in the multiple linear regression model with the long-axis cross-section light intensity in the test set with R_p, RMSEp, and RPD of 0.831 8, 0.074 3, and 1.916, respectively. This finding can provide a theoretical foundation and technical support to rapidly detect the salt content and yolk index in salted duck eggs.