Abstract: A dry suspension of Indigo Naturalis (IN) based on lactose-IN composite particles was designed by powder modification technology to meet the clinical needs of IN. The contact angle was used as an evaluation index to investigate the effects of the type of modifier lactose, the amount of lactose, and the co-grinding time of lactose and IN on the hydrophilicity of IN. The difference between IN before and after modification was compared through physical properties such as particle size and scanning electron microscope, as well as hydrophilic properties such as surface free energy and multiple light scattering. The optimal process of lactose-IN composite particles is as follows: after lactose is ground alone for 2 minutes, it is co-ground with IN at a ratio of 1∶1 for 6 minutes. The results of the investigation of powder properties show that the particle size d_0.9 of IN is reduced from 112.75 μm to 87.30 μm after modification. The BET and Langmuir specific surface areas decreased by 8.661 m²·g^-1 and 12.512 m²·g^-1, respectively. SEM shows that lactose is attached to the surface of modified IN (MIN); surface element analysis shows that Si, Ca, and Mg elements of MIN are smaller than IN, and O elements are larger. The infrared spectrum shows that the MIN possesses the characteristic peaks of both IN and lactose. Compared MIN with IN, the contact angle and the non-polar surface free energy decreased by 35.1° and 9.975 mJ·m^-2, respectively; the polar surface free energy and the surface free energy increased by 36.956 and 26.950 mJ·m^-2, respectively. The results of multiple light scattering showed that the light transmittance of MIN was 35% lower than that of IN, and the backscattered light intensity was increased by about 25%. Only one excipient was used to successfully prepare IN dry suspension with good wettability and suspending property, which provided a basis for the development of new preparations of IN.