The invention provides a device for extracting and trapping mercury isotopes in a solid sample, the device comprises a mercury isotope extraction unit and a mercury isotope trapping unit, the mercury isotope extraction unit comprises a solid sample boat, a quartz outer tube, a first heat source and a second heat source, one end of the quartz outer tube is connected with an oxygen inlet tube, and the other end of the quartz outer tube is connected with a gas outlet tube; one end of the oxygen inlet pipe is connected to the quartz outer pipe, the other end of the oxygen inlet pipe is connected to the mercury isotope trapping unit, the solid sample boat is arranged at one end, close to the oxygen inlet pipe, in the quartz outer pipe, the first heat source and the second heat source are located at the bottom of the quartz outer pipe, and a heating area of the first heat source is a corresponding area of the solid sample boat. And a heating area of the second heat source is a blank area in the quartz outer tube. The device is widely applicable to solid samples containing different types of mercury with large mercury content difference, complex combustion pyrolysis components of the samples and many interference factors, can accurately, efficiently, stably and conveniently trap mercury isotopes in the samples, and has the characteristics of low cost, easiness in operation and the like.