The reasonable level of organic fertilizer is important for the protection of soil fertility and grain production. Therefore, a field experiment was conducted to study the effects of pig manure replacing nitrogen fertilizer on soil organic nitrogen components under rice-wheat rotation, six treatments were designed which included no fertilization (T0), no nitrogen (T1), single application of chemical fertilizer (T2), 25% pig manure nitrogen and 75% chemical fertilizer nitrogen(T3), 50% pig manure nitrogen and 50% chemical fertilizer nitrogen (T4), 100% pig manure nitrogen (T5). The results showed that pig manure replacing nitrogen fertilizer increased total hydrolysable nitrogen, non-hydrolysable nitrogen and acid solution nitrogen of each component content. Compared with T0, in rice season, the contents of soil total hydrolysable nitrogen, amino acid nitrogen and hydrolysable unidentified nitrogen under T4 treatment increased by 17%, 8% and 133%, respectively; in wheat season, the contents of soil total hydrolysable nitrogen, amino acid nitrogen and hydrolysable unidentified nitrogen under T3 treatment increased by 11%, 8% and 127%, respectively, compared with T0 treatment; however, the effects of each treatment were not significant on the contents of ammonia nitrogen and amino sugar nitrogen both in rice season and wheat season. In general, in rice season 50% pig manure replacing nitrogen fertilizer and in wheat season 25% pig manure replacing nitrogen fertilizer can increase the contents of soil total hydrolysable nitrogen, amino acid nitrogen and hydrolysable unidentified nitrogen, thereby can increase soil nitrogen supplying capacity.