Surfactants and inorganic acids are usually added to fracturing fluids to improve CH4 desorption and diffusion by the wetting and corrosion effect. In this work, cocamidopropyl betaine (CAB) and H2SO4 were used to treat coal samples and then CH4 adsorption-desorption experiments and low-temperature liquid nitrogen experiments were carried out. The effects of CAB and H2SO4 and the composite solution on CH4 adsorption-desorption characteristics and pore structure of the coal samples were investigated. The results show that, after treated by the composite solution, the macropore volume of the coal samples increased while the specific surface area decreased, providing more channels for CBM diffusion and reducing CH4 adsorption sites. The decrease of fractal dimensions D1 and D2 indicates that the coal surface becomes smoother and the pore connectivity is enhanced. Therefore, the wetted-corroded coal samples had higher CH4 desorption rates and lower residual adsorption amounts compared to the coals treated with water and the single-component solution of CAB or H2SO4, and CH4 desorption rate of the wetted-corroded coal samples increases and the residual adsorption amount decreases as the acidity of the composite solution intensifies. This work will provide insights into the improvement of CBM desorption and diffusion using CAB and H2SO4 composite solutions.