NOVELTY - Preparing a flexible copper electrode pattern with a micrometer line width comprises: (a) cleaning and drying a flexible plastic substrate; (b) soaking the cleaned plastic substrate in a modified solution for 2-4 hours, taking out, cleaning and drying; (c) covering the modified plastic substrate under a light mask and irradiating by UV light; (d) placing the irradiated plastic substrate in a catalytic activation solution, taking, cleaning and drying; and (e) soaking the activated plastic substrate in copper chemical plating liquid, chemically plating, taking out, cleaning and drying.    USE - The flexible copper electrode pattern is useful in flexible transistor, flexible solar cell and flexible luminous device industries.    ADVANTAGE - The method: produces flexible copper electrode pattern having good precision, which is determined by the light mask and can achieve micrometer line width, can tolerate repeated folding, has high conductivity, durability and reliability; is preformed in a solution; does not require large instruments and an ultra-clean chamber; is suitable for large-scale production at lower costs; firmly combines the electrode pattern and the plastic substrate; and reduces the energy consumption.    DETAILED DESCRIPTION - Preparing a flexible copper electrode pattern with a micrometer line width comprises: (a) cleaning and drying a flexible plastic substrate; (b) soaking the cleaned plastic substrate in a modified solution for 2-4 hours, taking out, cleaning and drying; (c) covering the modified plastic substrate under a light mask and irradiating by UV light for 10-30 minutes; (d) placing the irradiated plastic substrate in a catalytic activation solution for 8-12 hours, taking, cleaning and drying; and (e) soaking the activated plastic substrate in copper chemical plating liquid, chemically plating at 15-25 degrees C for 20-30 minutes, taking out, cleaning and drying to obtain the product. The solute of the modified solution is 3-sulfydrylpropyl trimethoxy silane, 3-aminopropyltrimethoxy silane, 3-sulfydryl propyl triethoxysilane and 3-aminopropyl triethoxysilane. The solvent is methanol, ethanol, isopropanol or acetone. The amount of the modified solution is 0.01-5 wt.%. The catalytic activation solution comprises a solute, which is deionized water, palladium chloride (0.1-1 g/l), hydrochloric acid (1-5 g/l), trisodium citrate (1-5 g/l), potassium borohydride (0.5-1 g/l). The copper chemical plating solution comprises deionized water, copper sulfate (7-10 g/l), potassium sodium tartrate (30-40 g/l), sodium hydroxide (4-6 g/l), sodium hydroxide (2-3 g/l). The concentration of nickel chloride and formaldehyde is respectively 1-2 g/l and 2-3 g/l.