Photodegradation of pory[methyl(phenyl)silylene] (PMPSi) was studied by tow-temperature thermoluminescence and photoluminescence. It has been found that this process is nearly reversible at moderate UV exposure; the reverse reaction could be accelerated thermally. The activation energy of the annealing process was determined as 0.65 eV. Different character of the photadegradation was found under the excitation with 366 nm and 250-280 nm light at room temperature (i.e., within sigma-sigma* and pi-pi *transitions, respectively), sigma-sigma* excitation leads to the formation of deep charge carrier traps (E-t= 0.45 eV) of photodestructive origin which are associated with photoscission of Si bonds in the backbone. The presence of electron acceptor dopants strongly inhibits the trapping ability of these traps.