Abstract: In order to understand the effects of nitric oxide (NO) on the growth and development of porcine preantral follicle, we treated the follicles with different concentrations of sodium nitroprusside (SNP, 0, 0.001, 0.01, 0.1 and 1 mmol·L^-1), a nitric oxide donor. The results showed that the follicle diameter increased during in vitro culture, but there were no significant differences (P>0.05); the survival rate in 1 mmol·L^-1 SNP group was significantly lower than that in 1 μmol·L^-1 SNP group (61.61% vs 81.52%, P<0.05), but no significant differences were found between other treatments (P>0.05); the antrum formation rate in 1 μmol·L^-1 SNP group reached highest to 50% on day 4, and the rate in 1 μmol·L^-1 SNP group on day 6 was higher than that of 0.01 mmol·L^-1 SNP; In addition, the antrum formation rate in 1 μmol·L^-1 SNP group was significantly higher than that in 0.1 and 1 mmol·L^-1 SNP group (73.07% vs 50%, 47.62%, P<0.05). After 6 days′culutre, the oocyte normal rate in 1 mmol·L^-1 SNP group was significantly lower than that in 1 μmol·L^-1 SNP group (71.21% vs 48.18％，P<0.05), and there were no significant difference between other treatments (P>0.05). The recovery rate of cumulus cells oocyte complexes (COCs) in 1 μmol·L^-1 SNP group was significantly higher than that of control and any other treatments (37.27% vs 22.88%, 25.59%, 20.74% and 19.39%, P<0.05). The results indicated that during the in vitro culture of porcine preantral follicle, low concentration of NO which is released from SNP improves the oocyte growth, development and follicle antrum formation while high level of NO is toxic to follicle survival.