A process for simultaneous assay of chlorides and sulfides by low pressure ion exclusion chromatography is provided, and in said process an analytic apparatus comprising a sampling valve, a sampling loop, an ion exclusion column and an analytic detection flow path is used, and said process comprises the following steps: (1) in the analytic detection flow path, the mixture of developer R1 and developer R2 mixes with Eluent C and then enters into a reactor, and the mixing is continued under heating. The resulting mixture flows into the optical flow cell and a baseline is mapped accordingly; (2) a testing sample S flows into the sampling loop through a sample flow path and the sampling valve, and under the drive of Eluent C, flows into the ion exclusion column from the sampling loop, and enters into the analytic detection flow path through the ion exclusion column; developer R1 and developer R2 each enter into the analytic detection flow path through respective developer flow path and mix with each other in the analytic detection flow path. The mixture of developer R1 and developer R2 mixes with the Eluent C carrying the testing sample and then enters into the reactor, and the mixing is continued under heating and a reaction takes place. The reacted mixture flows into the optical flow cell and a spectrogram of the testing sample is mapped accordingly.