@@In this work, we developed a simple, but stable, rapid and high resolution isoelectric focusing (IEF) in array microdevice for protein or peptide separation. The most evident characteristic of microdevice of IEF was simply composed of the tiny anode and cathode vessels and 48 capillary columns of 20 mm length coated with cross-linked polyacrylamide gel (CPAG). Although simplicity, the array IEF microdevice hold the following advantages as unveiled by the experiments: (1) stable pH gradient and good reproducibility of IEF runs due to effective uniform controlling of electroosmotic flow (EOF) via CPAG coating in the manner of batch processing; (2) rapid IEF run of about 20 minutes due to the use of short capillary, different from 3-6 hours run in traditional gel-based IEF; (3) high resolution of protein bands achieved in only 20 mm long column, better than the separation in gel-based IEF with 70-170 mm gel strips. In addition, the developed method had high throughput, good linearity of pH gradient and low cost. Finally, the developed method was successfully used for high resolution separation of myoglobin and cytochrome (Cyt) C modified by chloroform.