  Infrared excess is an important probe of sub-stellar companions and/or debris
disks around white dwarfs (WDs). Such systems are still rare for in-depth
understanding of their formation and long-term evolution. One of the largest
spectroscopic surveys carried out by the Large sky Area Multi-Object fiber
Spectroscopic Telescope (LAMOST) recently released more than $3000$ WDs, a
significant fraction of which have not undergone excess search. Here we present
cross-correlation of LAMOST DR5 WD catalog with the Pan-STARRS, SDSS, UKIDSS,
2MASS, and {\it WISE}. By performing SED (spectral energy distribution) fitting
for 846 WDs with $WISE$ detections, we identify 50 candidates with infrared
excess, including 7 candidate WD+M dwarf binaries, 31 candidate WD+brown dwarf
(BD) binaries and 12 candidate WD+dust disk systems. 8 of the dust disk systems
are our new identifications. Utilizing a systematic survey with accurate
stellar parameters derived from spectral fitting, our work is an important
addition to previous searches for infrared excess from SDSS and {\it Gaia} WDs,
and provides a significant ($\gtrsim8\%$) complement to current database of WDs
with candidate BD companions and dust disks. The frequencies of WD+BD binaries
and WD+dust disk systems are constrained to be $\lesssim3.7\%$ and $\sim1.4\%$,
respectively. The properties of candidate dust disk systems are discussed. All
of our candidates require follow-up observations for confirmation owing to
limited spatial resolution of {\it WISE}.
