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 300μJ 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 10~6 and the rms energy stability is under 1.35%. The contrast ratio is higher than 10~8 within a scale of 20 ps before the main pulse. Consequently, the improvement factor of the signal contrast is approximately equal to the gain 10~6 outside the pump window. 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 10 ~ 6 and the rms energy stability is under 1.35%. The contrast ratio is higher than 10 ~ 8 within a scale of 20 ps before the main pulse. Consequently, the improvement factor of the signal contrast is approximately equal to the gain 10 ~ 6 outside the pump window.