This study was performed to prepare nano turmeric powder (NTP) by ultrafine grinding from raw turmeric powder (RTP). In addition, evaluate and compare the antioxidant activity of RTP and NTP extracts with Butylated hydroxytoluene (BHT), Ascorbic acid and α-tocopherol. The results revealed that ultrafine grinding has effectively milling the turmeric particles to nano-scale. Prepared turmeric nanoparticles were spherical in shape with particle size range from 25-148 nm. The prepared NTP showed decrease in water holding capacity after the grinding treatment. On the other hand, the swelling capacity of NTP was higher than those of RTP. The results of antioxidant activity conducted on successive extracts showed significantly (P≤0.05) increasing as affected by ultrafine grinding. Results of antioxidant activity carried out according to the DPPH^• radical scavenging showed that free radical scavenging activity of NTP exhibited significantly (P≤0.05) stronger radical scavenging activity compared to RTP. The IC₅₀ values of RTP and NTP were 21.45 and 7.82 (mg); respectively. Ultrafine grinding treatment significantly (P≤0.05) increased the radical scavenging abilities of NTP extracts on ABTS^•+ radicals 739.26 mM TE at concentration of (5 mg/ml), compared to 311.18 mM TE. The IC₅₀ values of RTP and NTP for ABTS^•+ were 237.75 and 442.35 mM TE/g; respectively. It means NTP was considered a special natural material rich in polyphenols with a strong antioxidant function.