Covalent cross-linking of carbon nanotubes (CNTs) is a useful way of transferring the unique properties of individual CNTs to macroscopic structures for a wide variety of applications. For elaborate engineering of the crosslinking reaction of CNTs, quantitative analysis of cross-linking reaction is imperative. We report here a universally applicable method to quantitatively analyze the cross-linking of CNTs by esterification. To distinguish the cross-linking reaction from the one-side reaction, where only one end of the linker reacts with a CNT, mass and molar balances were established based on thermogravimetric analysis data. This analysis revealed that approximately one in five linkers was involved in the cross-linking reaction. Qualitative characterizations such as Fourier transform infrared and Raman spectroscopy were also used to confirm the cross-linking reaction.