The invention discloses austenite heat-resistant valve steel and a manufacturing method thereof. The steel comprises the following components, by mass percentage, 0.45-0.55% of C, 0.08-0.45% of Si, 8.00-10.00% of Mn, 20.00-22.00% of Cr, 3.50-5.00% of Ni, no more than 0.30% of Cu, 0.80-1.50% of W, 0.45-0.55% of N, 1.80-2.50% of Nb, no more than 0.02% of Al, no more than 0.010% of Mg, 0.001-0.01% of Ca, 0.001-0.006% of B, and 0.005-0.020% of RE, with the balance being Fe and inevitable impurities, wherein C+N>=0.09, Nb/C is in a range of 2-5, and (Mn+Si)>=200. The manufacturing method mainly comprises smelting, casting, blooming, rolling, complete solution and aging treatment.