An ink for inkjet computer-to-plate and a preparation method of the same are provided. Calculated in mass percentage based on the total mass of the ink, the ink comprises 10%˜30% of cross-linkable resin, 10%˜35% of solvent with a low boiling point, 5%˜30% of poor solvent with a high boiling point and 5%˜75% of bulk solvent. The preparation method comprises the following steps: mixing the above components and agitating at room temperature; after the cross-linkable resin is dissolved, ball milling and filtrating to remove insoluble substance and/or impurities in the liquid obtained by the ball milling. The ink can be formed into an image by printing on the treated surface of aluminum plate using ink-jet printer, and after heat cured, it can form an image with a high resolution and be used to print directly on machine, thus reducing post treatment process and obtaining the plate of ink-jetting direct plate-making.