The invention provides a selenium-enriching milky slice and its preparation method. The selenium-enriching milky slice is prepared from, by weight, 0.1-5 parts of selenium extractive of nature selenium-enriching plant, 20-40 parts of milk powder, 20-40 parts of dried condensed milk, 1-10 parts of plant protein and 0-55 parts of excipient. The plant protein is plant embryo milk or soybean protein.The preparation method includes steps of weighing selenium extractive of nature selenium-enriching plant, milk powder, dried condensed milk, plant protein and excipient according to mixture ratio; mixing evenly and then sterilizing; laminating the mixture in a 100, 000 grade purifying workshop. The milky slice is high in organic selenium content, exact in dosage, high in bioavailability, rich in nutrition, safe and delicious, and convenient to eat.