We derive stellar parameters and abundances (`stellar labels) of 40,034 late-B and A-type main-sequence stars extracted from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope Medium Resolution Survey (LAMOST--MRS). The primary selection of our early-type sample was obtained from LAMOST Data Release 7 based on spectral line indices. We employed the Stellar LAbel Machine (SLAM) to derive their spectroscopic stellar parameters, drawing on Kurucz spectral synthesis models with 6000 K $< T_mathrm{eff} <$ 15,000 K and $-1$ dex $< mathrm{[M/H]} <$ 1 dex. For a signal-to-noise ratio of $sim 60$, the cross-validated scatter is $sim$75 K, 0.06 dex, 0.05 dex, and $sim 3.5,mathrm{km,s^{-1}}$ for $T_mathrm{eff}$, $log g$, [M/H], and $vsin i$, respectively. A comparison with objects with prior, known stellar labels shows great consistency for all stellar parameters, except for $log g$. Although this is an intrinsic caveat that comes from the MRSs narrow wavelength coverage, it only has a minor effect on estimates of the stellar rotation rates because of the decent spectral resolution and the profile-fitting method employed. The masses and ages of our early-type sample stars were inferred from non-rotating stellar evolution models. This paves the way for reviewing the properties of stellar rotation distributions as a function of stellar mass and age.
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