The Laiwu pig is famous for its excessively higher level of IMF content, however, the exact regulatory mechanism is still unknown. The intramuscular fat content (IMF) is an economically important traits in pigs, which is controlled by multiple genes and biological pathways. In the present study, we performed an integrated transcriptome-assisted label-free quantitative proteomic analysis of longissimus dorsi (LD) muscle in Laiwu pigs at the fastest IMF deposition stage. A total of 5074 unique proteins were identified and 191 were differentially abundant proteins (DAPs) (> 1.2-fold cutoff, p < 0.05), which were hierarchically clustered in the LD muscle over two developmental stages from 120 d to 240 d. Proteins participating in the regulation of lipolysis in adipocytes and AMPK signaling pathway were identified. Six proteins were analyzed using parallel reaction monitoring (PRM) to confirm the reliability of the TMT proteomic analysis. Association networks of differentially abundant proteins revealed that these DAPs were mainly involved in ribosome biosynthesis in eukaryotic species. A comparasion between transcriptomic (mRNA) and proteomic data revealed seven differentially expressed genes corresponding to DAPs. This study, for the first time, provides some data for the elucidation of the molecular mechanism of IMF deposition in pigs.