Abstract： Objective　To optimize the negative helical CT cholangiopancreatography (N-HCTCP) imaging parameters. Methods　By means of the water phantom, noise was obtained from 3 different milliamperes (110 mA, 170 mA, 240 mA), and low(AB10)-, medium(AB50)-, and high(AB91)-spatial resolution algorithms were compared respectively. 25 patients with obstructive pancreaticobiliary disease received non-contrast versus contrast scanning under the condition of the AB10. Then, the raw data from contrast scanning were reconstructed with the AB50. Their images of MinIPs and SSDs were evaluated respectively. Results　Among the 3 different mAs and the algorithms, the value of noise had significant differences (P＜0.05), and it was lowest under the condition of highest mA and lowest spatial resolution algorithm. The significant different results (P<0.001) were also showed between non-contrast and contrast scanning, and between AB10 and AB50. The image quality of the AB10 with contrast scanning was better than those with the AB50 and non-contrast scanning. Conclusion　By suppressing the noise, better images of N-HCTCP could be obtained by contrast scanning.