Developing early-heading wheat cultivars is an important breeding strategy for saving photo-terminal resources, and facilitating the multiple-cropping systems and annual grain yield. Psathyrostachys huashanica Keng (2n = 2x = 14, NsNs) is a potentially useful germplasm of early heading and maturation for wheat improvement. In this study, we found that a wheat–P. huashanica 7Ns disomic addition line, namely 18-1-5, showed earlier heading and earlier maturation than its wheat parents. Morphological observations of spike differentiation revealed that 18-1-5 developed distinctly faster than its wheat parents from the double ridge stage during spike development. To explore the potential molecular mechanisms on the early heading, we performed transcriptome analysis at four different developmental stages of 18-1-5 and its wheat parents. A total of 10,043 differentially expressed genes (DEGs) were identified during spike development. Gene Ontology (GO) enrichment analysis showed that these DEGs were linked to carbohydrate metabolic process, photosynthesis, response to abscisic acid, and ethylene-activated signaling pathway. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that these DEGs were mainly involved in plant hormone signal transduction (ARF, AUX/IAA, SAUR, DELLA, BRI1, and ETR), starch and sucrose metabolism (SUS1 and TPP), photosynthesis-antenna proteins (Lhc), and circadian rhythm (PRR37, FT, Hd3a, COL, and CDF) pathways. In addition, several DEGs annotated as transcription factors (TFs), such as bHLH, bZIP, MADS-box, MYB, NAC, SBP, WRKY, and NF-Y, may be related to flowering time. Our results provide valuable information for further studies on the regulatory mechanism, candidate genes, and genetic resources of early-heading breeding in wheat.