The polycondensation of terephthaloyl chloride and p-phenylene diamine was systematically studied．High molecular weight PPTA with ntnh=5一7 were prepared and the main factors influencing the solution polycondensation of 1

4-phenylene diamine with terephthaloyl chloride were studied in detail．Experimental reaults showed that the moisture content of the reaction system．reactant coneentration and volume ratio of mixed solvents have great influences on the inherent viscosity of poly-(1，4-phenyleneterephth'alamide) ob-rained．Highest ntnh was obtained at a reactant concentration of 0.3m/l in a mixed sol-vent HMPA/DMlAC ratio of 4/1 (by volume)；at a reactant concentration of 0.35m/l，in a mixed solvent(HMPA/NMP) of 7/3 and at a reactant concentration of 0.5m/l in a mixed solvent(HMPA/TIIF) of 9/1．The water content of the polymerization system must be strictly controlled to less than 100ppm．In the early stage of polyeondensation process the ninh of the polymer obtained in-creased rapidly with time．The system gelatinized within two or three minutes while the consumption of monomers reached 100％．The reaction of polycondensation con- tinued after gelati'on and the nthn of the obtained polymer increased appreciably．