The invention discloses a weight-loss health-care food which is prepared from the main raw materials of, by weight, 1-60% of a white kidney bean extract, 1-50% of L-malic acid, 1-65% of L-carnitine tartrate, and 1-40% of konjac powder. The invention also discloses a preparation method of the weight-loss health-care food. The method comprises the step that: the main materials of the white kidney bean extract, L-malic acid, L-carnitine tartrate, and konjac powder are well mixed, such that the health-care food with weight-loss function is obtained. With the health-care food, starchy substance absorption is inhibited, body metabolism is promoted, and energy conversion is promoted, such that fat consumption is increased, fat formation is prevented, and a weight-loss function is achieved. With the preparation method, absorption of nutrients such as proteins and vitamins is not influenced, diet control is not needed, and weight can be naturally controlled and reduced. The preparation method provided by the invention has the advantages of simple process, no high-temperature operation, convenient operation, and energy saving.