Reported herein is an introduction to an instructional mass spectrometer, which consists of six parts, an injection system, ion source, pulse accelerator, mass analyzer, detector, and vacuum system, for undergraduate-designed chem. anal. experimentsIn the experiment, students must manually assemble the instructional mass spectrometer from the building blocks and adjust parameters to deepen their understanding of the principles and structure of mass spectrometry.Then, using a homemade instructional mass spectrometer, they measure the sample to obtain its corresponding mass spectrum and deduce the chem. composition according to the mol. and fragment ions by analyzing the isotopes and relative abundances.We conducted practical instruction for undergraduate students majoring in chem.Students had significant gains in using the mass spectrometer, analyzing mass spectra, and assembling the instrument, showing high enthusiasm for the original experiments