A manufacturing method of an array substrate is provided in this invention, a protective layer for the channel is formed by magnetron sputtering and thermal annealing treatment with the oxygen concentration greater than 21%, at a temperature of 300˜400° C. and the material of the protection layer includes Al2O3. The present invention further includes an array substrate and a liquid crystal display panel with the array substrate. The present invention prevents the impurity such as hydrogen atom into the channel, and the quality of the protective layer prepared by the present invention is higher to ensure the electrical properties of the channel and process easy to be achieve and conducive to industrialization.