Effect of pentaerythritol di(monochlorophosphate) (SPDPC) on thermal stability of cured alkyd resin was studies. It was found that SPDPC addition decreases gel fraction content in alkyd coatings, especially if SPDPC concentration is lower than 15%. Moreover, SPDPC addition above 5% does not change swelling degree of pentaphtalic resin. It was found from thermogravimetric measurements that mass loss in SPDPC containing coatings is slower, and it is shifted towards higher temperatures in comparison with unmodified resin. Coatings with 15-30% SPDPC are distinguished by good thermal stability at temperatures above 400degreesC. It was also stated that SPDPC introduction into alkyd coatings causes violent lowering of strong exothermic effect in temperature range 400-500degreesC, which is characteristic of unmodified coating combustion.