Experimental investigations of nondegenerate ultrabroadband chirpedpulse optical parametric amplification have been carried out. Thegeneral mathematical expressions for evaluatingparametric bandwidth, gain and gain bandwidth for arbitrary three-wavemixing parametric amplifiers are presented. In our experiments, atype-I noncollinear phase-matched optical parametric amplifier based onlithium triborate, which was pumped by a 5-ns second harmonic pulsesfrom a Q-switched Nd:YAG operating at 10 Hz, seeded by a 14-fsTi:sapphire laser at 800 nm, was presented. The 0.85 nJ energy of inputchirped signal pulse with 57-FWHM has been amplified to 3.1 μJ at pumpintensity 3 GW/cm2, the corresponding parametric gainreached 3.6×103, the 53 nm-FWHM gain spectrum bandwidth ofoutput signal has been obtained. The large gain and broad gainbandwidth, which have been confirmed experimentally, provide greatpotentials to amplify efficiently the broad bandwidth femtosecond lightpulses to generate new extremes in power, intensity, and pulse durationusing optical parametric chirped pulse amplifiers pumped by powerfulnanosecond systems.