The combined application of woody peat with labile organic materials is an effective strategy for rapidly improving soil organic matter (SOM) and soil fertility in newly reclaimed lands. However, their decomposition dynamics, which can be greatly influenced by the residue-mixing effect, are not well understood. Therefore, this study investigated the decomposition characteristics and residue-mixing effect of woody peat, corn straw, organic manure, and their binary mixtures in a newly reclaimed saline-sodic soil through a 360-d incubation experiment. The results revealed that both straw and organic manure contained large amounts of O-alkyl carbon (C), leading to rapid decreases in their weight and organic C (OC) content during incubation. In contrast, the woody peat was rich in alkyl C and aromatic C, exhibiting the highest alkyl C/O-alkyl C (A/O-A) ratio and aromaticity. As a result, the woody peat only lost less than 6.4% OC and showed minimal changes in weight and total nitrogen content after one-year incubation, indicating strong degradation resistance in the saline-sodic soil. The combination of woody peat with corn straw or organic manure induced significant non-additive synergistic effects on their weight and OC losses, aromatic C, carbonyl C, A/O-A ratio, and aromaticity. This suggests that the addition of woody peat significantly slowed down the degradation of the mixtures and prolonged the retention of OC in soil. On the contrary, the mixing of corn straw and organic manure led to significant non-additive antagonistic effects on their weight and OC losses, indicating that their combination accelerated their decomposition. Consequently, this study suggests that, in contrast to the single application of various labile organic materials, the combined application of recalcitrant woody peat with labile organic materials can extend the presence of organic matter in soil, thereby promoting a sustained increase in both active and passive SOM contents and soil fertility.