A method for detecting mercury chloride and mercury bromide at same time comprises the steps of (1) setting detection conditions; (2) treating samples; (3) preparing mercury chloride and mercury bromide stock solutions; (4) performing spectral analysis; (5) calculating contents. By using gas chromatography-mass spectrometry, it is possible to specifically detect mercury chloride and mercury bromide in a biological sample rather than detect only the content of total mercury in the biological sample; detection sensitivity is improved, detection steps are greatly simplified, and time and cost are saved.