The invention relates to a cordyceps sinensis fluid medium and a preparation method thereof. The cordyceps sinensis fluid medium comprises the following materials by weight percent: 10-30% of jerusalem artichoke, 1-5% of potato, 1-5% of beef extract, 1-6% of fish meal, 0.03-0.08% of vitamin B1, 0.02-0.06% of riboflavin, 0.01-0.05% of folic acid, 0.05-0.1% of magnesium sulfate, 0.06-0.1% of sodium chloride, and the balance of water. The jerusalem artichoke powder is firstly used for the cordyceps sinensis fluid fermentation medium, an excellent technological effect is acquired, the quality of the obtained cordyceps sinensis is high, and active ingredients of the obtained cordyceps sinensis are rich.