The invention provides hard alloy and a preparation method thereof. The hard alloy comprises a WC hard phase and a binding phase; coarse crystal grains and fine crystal grains in the WC hard phase coexist and are distributed uniformly; the coarse crystal grains WC are plate strip-shaped; the length-width ratio of the coarse crystal grains WC is greater than 3:1; the binding phase is Co+Ni3Al. According to the hard alloy provided by the invention, the toughness of the alloy is improved on the premise that the hardness is maintained, and the alloy has excellent high-temperature comprehensive performance.