Abstract: Yu Weichu, Sun Tianxi, Li Shulian This paper introduces the design thinking, structure, principle, testing precision and applying domain of permeability gradient meter. Its key part is core holder with several pressure tap. It can test fluid pressure in each part of core by high precision pressure sensor, show data information by microcomputer and draw a series of curves. It can calculate core permeability according to inputting parameters, and then understand the relation of core permeability with depth after the core is treated by completion fluid, water plugging agent or acidizing fluid etc.. The obvious results have been obtained in field application. It provides a new evaluation method for study of formation protection.