The waste mud produced in geotechnical engineering construction has properties of high water content and poor dewatering character, so it is important to study how to improve the amount of dehydration. Various types of physical or chemistry conditioning were carried out in the tests to change the physicochemical nature of particle surface and components of waste mud to destroy the band colloid structure and reduce the affinity between water and colloid particles, thus the dewatering performance of waste mud can be improved. Based on the experimental analysis on the different types of inorganic materials and organic polymer flocculants, it is found that the dewatering effect of PAM for waste mud is superior to that of inorganic materials; and among cationic PAM, anionic PAM and nonionic PAM, cationic PAM is the best in dewatering performance.