The impact of time-domain properties about the signal pulse on spectrum and conversion efficiency after optical parametric chirped pulse amplification (OPCPA) is studied, based on coupled equations in YCOB crystal, when pump energy and pulse shape are certain. The energies of pump and signal pulse are 45 J and 500 mJ, and beam diameters are 60 mm and 50 mm, respectively, during the calculation. Pulse width of pump pulse is 3 ns, while signal′s is 1.2 ns. The numerical results show that signal spectrum amplified and conversion efficiency are related to time-domain properties of input signal pulse. The spectral full width at half maximum (FWHM) after OPCPA is broadened from 36 nm to 61 nm when the signal pulse as one order Gaussian pulse, but that of two order Gaussian pulse is just broadened to 47 nm. The order is higher, broadening is less. The FWHM keeps almost unchanged at 36 nm, compared with that before OPCPA when the signal pulse as five even higher order Gaussian function. And when the length of YCOB crystal is constant, conversion efficiency reaches 32% when the signal pulse as one order Gaussian pulse, with that of two order Gaussian pulse is only 25%. That of eight order Gaussian pulse or above changed little, remaining approximately 19%. Temporal characteristics of signal pulse make great fluence on the spectrum and conversion efficiency of the amplified pulse when the pump pulse and the length of the crystal are certain.