The present invention relates to an improved process for the preparation of ethers of dihydroartemisinin, more particularly artemether and arteether containing more than 99% of β isomer from dihydroartemisinin by reacting dihydroartemisinin with trialkyl orthoformate in the presence of a dry cation exchange resin with a moisture content < 3% in an alcoholic solvent at 0°C- 30°C. The product >99% pure β-isomer of artemether and arteether is obtained directly with simple isolation procedure. The dry cation exchange resin can be reused.
