To investigate the engineering properties of hydroxycellulose modified disintegrated carbonaceous mudstone, this study conducted tests on its unconfined compressive strength, properties under dry and wet cycles, and physical and chemical properties. The effects of dosage, curing time, and the number of dry and wet cycles on the mechanical, physical, and chemical properties of disintegrated carbonaceous mudstone were analyzed, and the micromechanisms of hydroxycellulose modified disintegrated carbonaceous mudstone were revealed with the help of a scanning electron microscope (SEM). The unconfined compressive strength of modified disintegrated carbonaceous mudstone showed a tendency to increase first and then decrease with the increase in hydroxycellulose dosage under fixed curing time. It reached the maximum when the dosage was 4%. When the dosage of hydroxycellulose kept unchanged, the unconfined compressive strength of modified disintegrated carbonaceous mudstone increased with the increase in curing time and tended to level off after curing for 14 d. The unconfined compressive strength of hydroxycellulose modified disintegrated carbonaceous mudstone conformed to the trend of the exponential function. The pH of modified disintegrated carbonaceous mudstone remained unchanged, while its TDS value, conductivity, and salinity decreased. Hydroxycellulose enhances the mechanical properties of disintegrated carbonaceous mudstone mainly by cementing particles and filling pores.