A coil-tube continuous flow reactor embedded with a special type of continuous spiral static mixing piece was designed and used for preparing nucleating agent intermediate diaryl phosphoryl chloride efficiently. At the flow rate ≥ 0.4 m/s (180 mL/min) and precipitation mass fraction ＜ 10%, the precipitation triethylamine hydrochloride could flow stably with the liquid phase in strong turbulent flow field, which successfully solved the serious clogging problem in reaction channel. The millimeter scale of the reactor maintained the great mass transfer characteristics. The rapid and uniform mixing of reactive materials could be conducted at high flow rates, and the throughput was greatly increased. The optimum synthesis process in this continuous flow reaction system was obtained: empty pipe was used in the last 20% section of the coil tube to reduce the overall pressure drop of the reaction system; T-jet was used to mix the reaction materials; residence time was 3.5 min and reaction temperature was 90 oC; n(diaryl phenol) : n(triethylamine) : n(POCl3) = 1 : 2.8 : 1.1; the initial feed concentration of diaryl phenol and POCl3 were 0.29 and 0.32 mol/L, respectively. The product yield increased from nearly 90% of batch synthesis to 96%, and the space time yield (STY) increased by 43~44 times.