Mass spectrometry is a high sensitivity, highly selective, high throughput analytical technique. It is well suited to characterize polar, high mass molecules. It is one of the prime analytical techniques to study proteins, to determine their molecular mass, their amino acid sequence and their post-translational modifications. The objective of the present article is to introduce the most important mass spectrometry based methods relevant for protein analysis, like ionization techniques, mass analyzers and tandem mass spectrometry. We shall also introduce ,,top-down" and ,,buttom-up" protein sequencing and protein quantitation as well.