The present disclosure provides a device and method for measuring viscosity of acid natural gas with high precision and a wide temperature range. The device is based on the theoretical basis of gas measurement of double-capillary method. Ground conditions (low temperature and low pressure) or formation conditions (high temperature and high pressure) can be simulated by presetting different temperatures and pressures. The viscosity change of acid gas with changes in temperature and pressure is measured. The device has fewer measuring steps, is easy to operate and has high precision, and can provide valid reference data for actual projects or experiments.