We demonstrate a novel picosecond optical parametric preamplification to generate high-stability,high-energy and high-contrast seed pulses.The 5 ps seed pulse is amplified from 60 pJ to 300 μJ with an 8.6 ps/ 3 mJ pump laser in a signal stage of short pulse non-collinear optical parametric chirped pulse amplification.The total gain is more than 106 and the rms energy stability is under 1.35％.The contrast ratio is higher than 108 within a scale of 20ps before the main pulse.Consequently,the improvement factor of the signal contrast is approximately equal to the gain 106 outside the pump window.