In this paper, a stepped copper microcolumn array was fabricated based on the micro-electroforming process of THB–151N photoresist. In order to solve the problem of difficult development of 20 μm micro-blind hole and film retention at the bottom during THB–151N photoresist development, a submerged bidirectional megasonic assisted development method was proposed. The influence of megasonic power density and aspect ratio of micro-blind hole on mass transfer process of developer was simulated. The megasonic power density and aspect ratio of micro-blind hole were optimized, and the megasonic assisted development was studied experimentally. At the same time, aiming at the poor verticality of sidewall of the micro-blind hole due to inappropriate exposure dose of THB–151N film，the effect of exposure dose on the verticality of sidewall of the micro-blind hole was discussed by lithography experiment，the empirical equation of preferred exposure dose and film thickness was fitted. On the basis of the above technological methods and experimental study, 4×6 stepped copper microcolumn arrays with a height of 300 μm, overall aspect ratio of 15∶1 and minimum side length of 20 μm were fabricated.