The general acidification technology of horizontal wells provides a simple and important method of stimulation for carbonate gas reservoirs. The common acidization methods were divided into two major categories: matrix acidification and fracturing acidification. To determine the best stimulation method of horizontal wells between acid fracturing and matrix acidizing, it is significant to achieve the efficient exploitation of reservoirs and optimization of process program. A dimensionless gas production index formula was obtained for horizontal well acidizing in carbonate gas reservoir. Also, a carbonate-acid-stimulation coefficient model was established to optimize the general method of acidification for the horizontal wells in carbonate gas reservoirs. Then, the influence of geological and engineering factors on the acidization increase coefficient was analyzed. Finally, field verification and application were conducted. The conclusions are as follows. When the carbonate-acid-stimulation coefficient R_JH > 1, the productivity of matrix acidizing wells exceeds that of fractured acidizing wells. When R_JH < 1, the productivity of fractured acidizing wells is higher compared to matrix acidizing wells. A higher permeability anisotropy coefficient increases, the number of fracturing fractures and the amount of acid fluid, but reduces the carbonate-acid-stimulation coefficient. The increase in porosity and horizontal length lead, to a higher carbonate-acid-stimulation coefficient. When the porosity of the gas reservoir falls below 7.3%, the productivity of the fractured acidizing well is improved. When the length of the horizontal section is 500 m and the number of fracturing fractures exceeds 4, the carbonate-acid-stimulation coefficient R_JH < 1, and the productivity of the fractured acidizing well is improved. When the total volume of acid solution injected is 600 m³, the productivity of fractured acidizing well reaches a higher level than when the acid-solution volumetric dissolving power X > 0.08. As verified in the carbonate reservoirs located in the northeastern Sichuan block, the production increase effect produced by using the carbonate-acid-stimulation coefficient method is significant after process optimization. Therefore, a theoretical guidance is provided in this paper for optimizing the acidification method of horizontal wells in carbonate gas reservoirs.