There is lack of understanding on controlling of mechanical properties of moisture-curing PU/MF microcapsules which limited its further application. PU/MF microcapsules containing a core of isophorone diisocyanate (IPDI) were prepared with different chain extenders, polyetheramine D400, H2O, triethylenetetramine and polyetheramine (PEA) D230 by following a two-step synthesis method in this study. Fourier transform infra-red (FTIR) spectroscopy, Malvern particle sizing, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). And micromanipulation technique was used to identify chemical bonds in the shell, size distributions, structure, thickness, and mechanical properties of microcapsules. The results show that PU/MF microcapsules were successfully prepared. Tr increased from 46.4 +/- 13.9 N/m to 75.8 +/- 23.3 N/m when extender changed from D400 to D230. And the Tr increased from 51.3 +/- 14.1 to 94.8 +/- 17.5 N/m when the swelling time increased from 1 to 3h. Morphologies of the shell were utilised to understand the mechanism of reactions in forming the shell materials.