Intensity changes of secondary ions from Poly (methyl methacrylate) (PMMA) with ion bombardment has been investigated by time-of-flight secondary ion mass spectrometry (TOF-SIMS). The “dose profiles” of several ion species, which were recorded as intensity variations versus primary ion dose, were observed. It was found that the profile have various tendencies over a range of ion dosage from 10¹² to 2×10¹⁴ ions/cm². By using a high mass resolution TOF-instrument, the closely located mass peaks such as C₃H₇⁺ and C₂H₃O⁺ at 43 amu were found to show different intensity change for different ion dosages. The relationship between the observed secondary ion intensities and bond breaking was discussed with referenced to the bond orders obtained by a semi-empirical MO calculation. It was found that the secondary ion formation reflects the bond strength of the analyzed polymer and the stability of the formed ions, and that the rearrangement processes may also have some influences on the detected ion intensities.