Using satellite remote sensing technology to monitor heavy metals in water is of great research significance. However, due to the low content of heavy metals in natural water, the feasibility of remote sensing inversion is still doubted by the academic community, resulting in relatively slow development in this field. Because of this, taking the retrieval of iron sulfate concentration in water by the Chinese HJ-1A Satellite Hyperspectral Imager (HSI) as an example, the remote sensing sensitivity analysis model (DDE model) was used to numerically simulate the lower limit concentration spectrums in remote sensing inversion of iron sulfate under the background of four kinds of water, including: theoretical clear deep water and three kinds of common natural water: eutrophic water, turbid water and heavy metal polluted water. The minimum value of the remote sensing inversion lowers the limit concentration, and its wavelength is given. The variation pattern of remote sensing sensitivity under the background of different kinds of water is then analyzed. The research results found that under the background of different kinds of water, the simulated minimum lower limit concentration of iron sulfate and its wavelength position changed. Under the background of theoretically clear deep water, the minimum lower limit concentration is 4.63×10-4 mg·L-1, appearing at 468.530 nm (the fifth band of the HSI sensor, abbreviated as Band 5, the same below). After expanding to the minimum 10% increment, the covered band range is 460.040~479.600 nm (Band 1—10). However, the lower limit concentration value no longer exists in the wavelength range 721.605~951.540 nm (Band 81—115). Similarly, under the background of three kinds of natural water: eutrophic water, turbid water, and heavy metal polluted water, the minimum lower limit concentrations are: 6.30×10-2, 2.78×10-2, and 1.64×10-1 mg·L-1; the corresponding wavelengths are: 577.865 nm (Band 46), 587.900 nm (Band 49), 669.285 nm (Band 70); the corresponding coverage band ranges after expanding the minimum value by 10% are: 555.725~587.900 nm (Band 39—49), 568.160~612.740 nm (Band 43—56), 627.895~687.410 nm (Band 60—74). The above characteristic bands are all important references for the future sensitive band collection of iron sulfate remote sensing inversion models. The relationship between the minimum lower limit concentration under the background of four kinds of water is: theoretical clear deep water<