An artificial diet for ghost moth larvae and a preparation method thereof. The artificial diet comprises root of Polygonum viviparum, soybean powder, bran, yeast powder, sucrose, casein, agar, water, choline chloride, ascorbic acid, sorbic acid, nipagin and multivitamin. After being fed for 60 days, third-instar larvae fed with the artificial diet showed an average survival rate of up to 92.67%, higher than those fed with carrots with an average survival rate of 90.33%. After being fed for 140 days, the larvae fed with the artificial diet showed an average survival rate of up to 86.67%, significantly higher than those fed with carrots with an average survival rate of 73.67%. Also, the larvae fed with the artificial diet showed significant increase in body weight, without the contamination of bacterium and fungi.