The invention provides a method for improving the direct current transmission capacity of a direct current fault steady-state voltage constraint. The method comprises steps of step 1, acquiring a direct current transmission power value P1 according to a steady-state voltage fluctuating value deltaV, a safety control generator tripping strategy and a direct current reactive swapping control threshold value of a power grid; step 2, if a direct current sending requirement power P is greater than P1, performing optimization and adjustment on the direct current reactive swapping control threshold value; step 3, acquiring a direct current transmission power value P2 of the power grid with the adjusted direct current reactive swapping control threshold value, and if P is greater than P2, performing combined tripping operation on a no-load circuit and a low voltage capacitor of the power grid; step 4, acquiring a direct current transmission power value P3 of the power grid after being subjected to combined tripping operation, and if P is greater than P3, performing direct current operation according to the direct current transmission power value P3. Compared with the prior art, the method for improving the direct current transmission capacity of the direct current fault steady-state voltage constraint provided by the invention can be used for increasing the electricity generating efficiency of a direct current matched power plant, reducing the short power supply in the peak period in a direct current receiving end area, and greatly improving the extra-high voltage direct current transmission capacity.