A means to successfully fabricate highly reproducible SrTiO3 step substrates for high Tc dc-Supercon-ducting Quantum Interference Devices (dc-SQUIDs) by micromachining is reported in this paper. At optimized Ar ion milling conditions, an inclined angle from 45 to 50° and a laid angle from 30 to 45°, the highest step angles can be obtained. Under strict process control, the profile of the Nb mask film is clean and sharp. The fabricated step angles are about 71° with steep and flawless topography. The step substrate yield for YBa2Cu3O7-x Josephson step edge junction dc-SQUIDs is 75%. The variation of junction resistance and critical current is ±28.6% and ±42.4% respectively.