Pure perovskite-type LaTaON2 crystal powders with high crystallinity were synthesized in supercritical ammonia using sodium amide as a flux. The synthesis temperature for this new method is 873 K., approximately 300 K lower than that for previous methods. The obtained powders have a pseudocubic lattice with a lattice constant of alpha = 0.4049 nm, which is in good agreement with the reported value.