The invention discloses a manufacturing method of an age-hardened thin-strip casting low-carbon microalloyed steel strip. The method comprises the following steps: 1) casting a cast strip with thickness of 1-5mm in a dual-roller continuous casting machine, wherein the weight percents of the components are as follows: 0.01-0.25% of C, not more than 0.4% of Si, 0.6-2.0% of Mn, not more than 0.015% of P, not more than 0.01% of S, and not more than 0.012% of N; furthermore, the cast strip further comprises at least one of Nb, V, Ti, and Mo in the following weight percent: 0.005-0.1% of Nb, 0.005-0.1% of V, 0.005-0.1% of Ti, and 0.05-0.5% of Mo, and the balance of Fe and unavoidable impurities; 2) cooling the cast strip, wherein the cooling rate is more than 20 DEG C / s; 3) hot-rolling at 1050-1250 DEG C, wherein the reduction rate is 20-50%, and the deformation rate is more than 20s-1; 4) cooling, wherein the cooling rate is 10-80 DEG C / s; 5) reeling at 550-700 DEG C; 6) performing age-hardening treatment, wherein the age-hardening temperature is 500-800 DEG C, and the heating time is 0.1-30 minutes. The austenite online recrystallization of the cast strip after hot-rolling is realized, the microstructure of the obtained steel strip is composed of fine polygonal ferrite and a pearlite, the structure comprises nanoscale precipitation such niobium carbonitride, and the high strength and extensibility are obtained.