This paper proposes a kind of seawater pH standard material more suitable for the measurement of pH in seawater, and studies the methods of preparation and setting method of small batch process for the preparation of the standard material. The pH value in seawater reference material determined by spectrophotometry is carried out to evaluate the homogeneity and stability of the seawater pH standard material prepared by F test and t test method. The experimental results show that both homogeneity and stability, in six month at room temperature, of this seawater pH standard material in artificial seawater are good.