In this paper, we synthesized a new kind of dual functional nitrogen- and sulfur-co-doped carbon dots(C-dots) which could be applied as the fluorescent temperature sensor and the probe of trace amounts of Fe³⁺ions via an one-pot facile hydrothermal approach from acrylic acid and methionine. The obtained C-dots with the average diameter of 2.3 nm manifested colorful fluorescence, good-solubility and attractive optical stability. The fluorescence lifetime is 7.92 ns. Although the quantum yield is 10.55%, the fluorescence can be fleetly and selectively quenched by Fe³⁺ions. The detection limit was as low as 1.72 nM. In addition, high ionic strength, mild acids and alkaline only own a small impact on the fluorescence intensity of the C-dots. Furthermore, the C-dots could be deemed as a temperature sensor with significant reversibility, sensitivity and linearity. Meanwhile, the C-dots also possessed great recoverable and thermal stable fluorescence as expected.