  Nuclear magnetic resonance (NMR) technique benefits from high magnetic field
not only due to the field-enhanced measurement sensitivity and resolution, but
also because it is a powerful tool to investigate field-induced physics in
modern material science. In this study, we successfully performed NMR
measurements in high flat-top pulsed magnetic field (FTPMF) up to 40 T. A
two-stage corrected FTPMF with fluctuation less than 10 mT and duration longer
than 9 ms was established. Besides, a Giga-Hz NMR spectrometer and a sample
probe suitable for pulsed-field condition were developed. Both
free-induction-decay and spin-echo sequences were exploited for the
measurements. The derived $^{93}$Nb NMR results show that the stability and
homogeneity of the FTPMF reach an order of 10$^2$ ppm / 10 ms and 10$^2$ ppm /
10 mm$^3$ respectively, which is approaching a degree of maturity for some
researches on condensed matter physics.
