The thermoelectric effect in two-dimensional materials is one of the cutting-edge research directions in condensed matter physics, and the magnitude of the micro-area thermal field gradient in two-dimensional thermoelectric devices plays a decisive role in the strength of the thermoelectric signal. This article uses COMSOL simulation software and uses a grid partitioning method that combines quadrilateral grid and swept grid, and simulates the thermal field distribution in two-dimensional thermoelectric devices. By comparing the simulation results of thermal field distribution under different heating wire shapes, lengths, thicknesses, widths, and heating currents, etc., it is found that the temperature gradient generated by rectangular heating wires is the most significant, which reveals the law that the temperature gradient decays with the distance from the heating wire as an inverse proportional function, and solves the technical problem of how to obtain a large temperature gradient on the sample in the thermoelectric effect detection experiment of two-dimensional materials. This article will not only provide strong guidance for the design and preparation of micro-nano structures such as heating wires in two-dimensional thermoelectric devices, but also has important significance for improving thermoelectric conversion efficiency and solving the heat dissipation problem of highly-integrated mictro-nano devices.