A method for measuring pH, comprising the following steps: with amide protons as an endogenous contrast agent, providing a plurality of amide proton solutions with different pH, wherein the pH of each of the amide proton solution is known; for each of the plurality of amide proton solutions, measuring a chemical change saturation transfer effect ratio R of amide protons under different saturation powers; establishing a function relation between the known pH and the measured R of the plurality of amide proton solutions; and finally calculating the desired pH according to experimentally measured Ri and the function relation, wherein Ri is a chemical exchange saturation transfer effect ratio of amide protons of a phantom to be tested or a tissue to be tested under different saturation pulse intensities; wherein, R is determined by R={(M 0 -M S1)×M S2}/{(M 0 -M S2)×M S1}, wherein M 0 is a signal amplitude when no saturation pulse is applied, M S1 and M S2 are chemical exchange saturation transfer effects when the saturation powers are ω 1 and ω 2, respectively; M S1 is determined by M S1 ={M S1 (-3.5 ppm)-M S1 (+3.5 ppm)}/M 0, wherein M 0 is a signal amplitude when no saturation pulse is applied, M S1 (-3.5 ppm) and M S1 (+3.5 ppm) are signal amplitudes at -3.5 ppm and +3.5 ppm when a saturation pulse is applied, respectively; and M S2 is determined by M S2 ={M S2 (-3.5 ppm)-M S2 (+3.5 ppm)}/M 0; wherein M 0 is a signal amplitude when no saturation pulse is applied, and M S2 (-3.5 ppm) and M S2 (+3.5 ppm) are signal amplitudes at -3.5 ppm and +3.5 ppm when a saturation pulse is applied, respectively; and the measurement of R of different pH-known amide proton solutions and the measurement of Ri are performed at the same experimental temperature and under the same imaging conditions. with amide protons as an endogenous contrast agent, providing a plurality of amide proton solutions with different pH, wherein the pH of each of the amide proton solution is known; for each of the plurality of amide proton solutions, measuring a chemical change saturation transfer effect ratio R of amide protons under different saturation powers; establishing a function relation between the known pH and the measured R of the plurality of amide proton solutions; and finally calculating the desired pH according to experimentally measured Ri and the function relation, wherein Ri is a chemical exchange saturation transfer effect ratio of amide protons of a phantom to be tested or a tissue to be tested under different saturation pulse intensities; wherein, R is determined by R={(M 0 -M S1)×M S2}/{(M 0 -M S2)×M S1}, wherein M 0 is a signal amplitude when no saturation pulse is applied, M S1 and M S2 are chemical exchange saturation transfer effects when the saturation powers are ω 1 and ω 2, respectively; M S1 is determined by M S1 ={M S1 (-3.5 ppm)-M S1 (+3.5 ppm)}/M 0, wherein M 0 is a signal amplitude when no saturation pulse is applied, M S1 (-3.5 ppm) and M S1 (+3.5 ppm) are signal amplitudes at -3.5 ppm and +3.5 ppm when a saturation pulse is applied, respectively; and M S2 is determined by M S2 ={M S2 (-3.5 ppm)-M S2 (+3.5 ppm)}/M 0; wherein M 0 is a signal amplitude when no saturation pulse is applied, and M S2 (-3.5 ppm) and M S2 (+3.5 ppm) are signal amplitudes at -3.5 ppm and +3.5 ppm when a saturation pulse is applied, respectively; and the measurement of R of different pH-known amide proton solutions and the measurement of Ri are performed at the same experimental temperature and under the same imaging conditions.