The invention aims at providing ultrahigh-strength and high-toughness maraging steel and application thereof. The ultrahigh-strength and high-toughness maraging steel comprises the following chemicalcomponents of, by weight percentage, less than or equal to 0.005% of C, 17.5-18.5% of Ni, 15.5-16.5% of Co, 6.8-7.2% of Mo, 1.3-1.7% of Ti, less than or equal to 0.004% of O and N, less than or equalto 0.005% of P, less than or equal to 0.005% of S, and the balance Fe. The service life of a gradient strengthening maraging steel firing pin prepared by adopting the maraging steel is 10 times that of a firing pin made of a traditional material, and the gradient strengthening maraging steel firing pin has the excellent using performance and has a broad application prospect.