Abstract: The total ion intensities of the metallothioneins(MTs) increase from pH 7 to 3. The use of electrospray mass spectrometry render it possible to acquire molecular and chemical binding information of the metallothioneins at different pH condition. The result shows that pH is the primary factor to determine the zinc combind to metallothioneins. Metallothioneins are conbined with four zinc at pH 4.0 while none zinc is found to be conbined to the protein at pH 3.0.