Oxide dispersion strengthened (ODS) steels are being developed as a promising structural material for next-generation nuclear energy systems, due to its excellent resistance to both irradiation damage and high-temperature creep. In this work, the mechanical alloying (MA) and hot isostatic pressing (HIP) technologies were used to prepare a ODS low-activation steel, based on the China low activation martensitic (CLAM) steel. SEM, XRD analysis and EPMA were used to examine the particle size, alloying element distribution and lattice distortion of the ball-milled powders. In order to obtain uniform powders, CLAM powders with 0.3%Y₂O₃ particles should be milled with hard steel balls of 6 mm in diameter for 50 h in Ar protective atmosphere, and the ball-to-powder weight ratio at 10∶1. The microstructure of well-prepared ODS-CLAM steel was stable till 1200 ℃ for 1 h, with grain size of 50~60 mm and martensitic lath width of 200 nm, meanwhile, the Y₂O₃ particles could still be found in the steel matrix.