The invention discloses a device for testing solubility of weak acid gas in an alkalinity absorption liquid, and belongs to the fields like gas absorption and separation and petrochemical industry, and the device is suitable for detesting an equilibrium solubility curve of the weak acid gas under different gas partial pressures and different temperatures. The device is composed of a gas transmission system, a reaction tank, a temperature control system, a sampling system, a gas partial pressure measuring system, a liquid sample analytic system and a gas volume measuring system, wherein the stainless steel reaction tank can increase the measurement range of the gas partial pressure, gas and liquid respectively control temperature so that the temperature is uniform and the use of a magnetic stirrer becomes possible, an intelligent instrument is utilized to carry out temperature control with high precision and pressure display, an acid hydrolysis method is adopted to analyze a liquid sample so as to obtain the solubility, the gas is utilized to blow down the liquid remained at the pipeline in the last experiment and the precision is improved, a eudiometer is adopted as a tool for measuring the gas volume, the measuring precision of the gas volume is guaranteed, the experimental result is more stable and reliable. The device provided by the invention has the advantages that the property is stable and reliable, and the device is simple and convenient.