The invention discloses cooked pseudo-ginseng. By weight, the total saponin content is 6.0-12.0%, and the sum of the content of the low-grade saponin in the transformation accounts for 40-90% of the total saponins of the cooked pseudo-ginseng. Inherent saponins in pseudo-ginseng contain ginsenoside R1, ginsenoside Rg1, and ginsenoside Rb1, the low-grade saponins generated by transformation contains ginsenoside 20 (S)-Rh1, ginsenoside 20 (R)-Rh1, ginsenoside Rd, ginsenoside Rk3, ginsenoside Rh4, ginsenoside 20 (S)-Rg3, ginsenoside 20(R)-Rg3, ginsenoside Rk1, and ginsenoside Rg5. The invention also discloses a preparation method of the cooked pseudo-ginseng. By precisely controlling the water addition, processing temperature and processing time, the cooked pseudo-ginseng having a certain saponin and the proportion thereof is obtained. The cooked pseudo-ginseng is rich in low-grade saponins that rarely exists in the dried pseudo-ginseng and can improve the immunity and the anti-tumor effect.