Synopsisp-Cresol was converted into 2,3,5,fXetrabromocresol by A1C13 catalyst bromination, and then further brominated to 4-hydroxy-2,3,5,6-tetrabromobenzyl bromide (HTBBB) in benzene by light. HTBBB reacted easily with trialkyl phosphite to produce 4-hydroxy-2,3,5,6-tetrabromobenzyl phosphonates (HTBBPs) in solvents. Although the reaction of HTBBB with triaryl phosphite was slower than that with trialkyl phosphite, it does produce corresponding phosphonate with ease. Except for DMF, DMAc, chloroform, and tetrahydrofuran, HTBBP was difficult to dissolve in ordinary organic solvents. Of all the synthesized HTBBP, dimethyl hydroxy-2,3,5,6-tetrabromobenzyl phosphonate showed the poorest solubility. With the addition of these new compounds containing bromine and phosphorus atoms to HIPS as flame retardants, the results of oxygen index measurement showed that the flame resistance of these compounds was greater than the additive effect of the two corresponding individual brominated compound and phosphoruscontaining compound. It means that these new compounds seem to act synergistically as flame retardants in HIPS. Simultaneous addition of bominated compound and phosphoruscontaining compound to HIPS ends up with a similar effect as mentioned above, but the new compounds can prevent the exclusion of phosphoruscontaining compound from polymer matrix.