  From previous samples of Red Supergiants (RSGs) by various groups, 191
objects are assembled to compose a large sample of RSG candidates in LMC. For
189 of them, the identity as a RSG is verified by their brightness and color
indexes in several near- and mid-infrared bands related to the 2MASS JHKs bands
and the Spitzer/IRAC and Spitzer/MIPS bands. From the visual time-series
photometric observations by the ASAS and MACHO projects which cover nearly 8-10
years, the period and amplitude of light variation are analyzed carefully using
both the PDM and Period04 methods. According to the properties of light
variation, these objects are classified into five categories: (1) 20 objects
are saturated in photometry or located in crowded stellar field with poor
photometric results, (2) 35 objects with too complex variation to have any
certain period, (3) 23 objects with irregular variation, (4) 16 objects with
semi-regular variation, and (5) 95 objects with Long Secondary Period (LSP)
among which 31 have distinguishable short period, and 51 have a long period
shorter than 3000 days that can be determined with reasonable accuracy. For the
semi-regular variables and the LSP variables with distinguishable short period,
the period-luminosity relation is analyzed in the visual, near-infrared and
mid-infrared bands. It is found that the P-L relation is tight in the infrared
bands such as the 2MASS JHKs bands and the Spitzer/IRAC bands, in particular in
the Spitzer/IRAC [3.6] and [4.5] bands; meanwhile, the P-L relation is
relatively sparse in the V band which may be caused by the inhomogeneous
interstellar extinction. The results are compared with others' P-L
relationships for RSGs and the P-L sequences of red giants in LMC.
