The invention discloses a method for preparing black color paste suitable for producing viscose tinting threads, which comprises the following process steps: preparing mixed solution, namely adding dispersant, anti-sinking agent and blue color paste into desalted water, adjusting the pH value of the mixed solution to between 9.0 and 9.5, and then adding carbon powder into the mixed solution to form emulsified mixed solution, wherein the desalted water accounts for 77.68 to 78.21 percent of the total weight of the emulsified mixed solution, the dispersant accounts for 2.0 to 4.0 percent of thetotal weight of the emulsified mixed solution, the anti-sinking agent accounts for 0.5 to 1.5 percent of the total weight of the emulsified mixed solution, the blue color paste accounts for 2.4 to 3.2 percent of the total weight of the emulsified mixed solution and the carbon powder accounts for 15 to 15.5 percent of the total weight of the emulsified mixed solution; grinding the mixed solution added with the carbon powder for at least 8 hours, and controlling the temperature of the mixed solution to between 26 and 30 DEG C; and filtering the mixed solution. The color paste prepared by the method has good dispersion effect, nearly has no precipitation phenomenon, and has good filtering effect; after the color paste is mixed with the viscose, the filtering effect is greatly improved; and the color paste has good spinning property, the chrominance of the threads tends to blue light, and the prominent problem of color paste raw material supply contradiction is solved.