The invention relates to a process technology method for efficient and low-cost converter production of ultra-low phosphorus liquid steel. According to the method, liquid steel with a temperature of 1260-1350 DEG C is added to a converter, wherein P content in the liquid steel is less than or equal to 0.11%, Si content in the liquid steel is 0.3-0.5%, and Mn content in the liquid steel is 0.3-0.6%; a slag material is added, argon gas is blown from the bottom, oxygen gas is blown from the top, and then the 1/3-1/2 of the slag is removed, wherein the flow rate of the argon gas is more than or equal to 0.07 Nm<3./t.min, the pressure of the oxygen gas is less than or equal to 0.8 MPa, the bath temperature is less than or equal to 1450 DEG C, and the early stage converting time is 7-10 minutes; in the middle stage, a high lance position operation is adopted, the slag material is complementally added, and then 40-60% of the slag is removed, wherein the C content in the liquid steel is 0.30-0.60%, and the temperature is 1520-1560 DEG C; in the later stage, per ton of the steel is complementally added with 2-5 kg of lime and 2-5 kg of a cooling agent, a large amount of the argon gas is blown from the bottom, a stirring treatment is performed for more than or equal to 1.5 minutes, and the steel is discharged when the end point C content is 0.025-0.08% and the temperature is 1600-1630 DEG C. According to the present invention the ultra-low phosphorus liquid steel with the phosphorus content less than or equal to 50 ppm is produced.