The piston guide and magnet assembly for the KRISS watt balance were tested. The velocity of the piston guide was controlled within 4×10-3 at the velocity of 2 mm s-1 using a linear motor and linear encoder feedback. The magnet assembly which consists of two permanent magnet rings and closed yokes was fabricated. B-field at the air gap of 25 mm was measured using a Hall probe. The B-field uniformity was within 5×10-4 over the vertical distance of 24 mm