The TAPPI T 529 standard specifies a nondestructive detection method for the pH value of paper surfaces, which is suitable for the measurement of hydrogen ion concentration on paper surfaces such as books and documents. This method uses pH test paper or pH Meter to measure its acid alkalinity by adding a small amount of deionized water dropwise on the paper surface. Compared with traditional cold extraction methods and thermal extraction methods, this method avoids damage to paper, and is especially suitable for evaluating the durability and preservation performance of paper. It is widely used in libraries, archives and the paper industry, providing a scientific basis for paper quality control and optimization of preservation conditions.