The invention discloses a method for extracting ammonium molybdate from a molybdenum contained waste liquid, which comprises the following steps: adding concentrated sulphuric acid into the molybdenum contained waste liquid so as to adjust the pH value to be 0.1-3.5, and obtaining the molybdenum contained waste liquid through clarification; adding the molybdenum contained waste liquid into an N235/octanol/sulfonated kerosene extraction system for molybdenum extraction, wherein the phase ratio O/A is equal to 1/(1-3); performing extraction for 10 minutes to obtain molybdenum contained load organic phase; adding the molybdenum contained load organic phase into a load organic phase, wherein the sulfuric acid with concentration of 0.1-1 mol/L is adopted, and the phase ratio O/A is equal to (3.12-5)/1; performing extraction and washing for 10 minutes; performing cross flow washing, wherein the washed organic phase is subjected to reverse extraction of the molybdenum in the next step; adding aqua ammonia with concentration of 5-12 mol/L, wherein the phase ratio O/A is equal to (3.3-3.6)/1; and performing reverse extraction for 10 minutes to obtain the ammonium molybdate solution. According to the invention, the extraction for precious rhenium is not damaged, the same extraction system can be adopted, the secondary impurity-removing rate is high, and the molybdenum concentration can be improved quickly, which in turn facilitates the extraction of molybdenum.