[Objectives]  To compare metabolic differences between diapausing (Dpre) and non-diapausing Trichogramma dendrolimi prepupae (NDpre) in order to better understand the diapause mechanism of this species. [Methods]  Liquid Chromatography-Mass Spectrometry (LC-MS) was used for metabonomic analysis. PCA, PLS-DA and OPLS-DA were used for model analysis and statistical tests. Differences in metabolites between treatment groups were compared using the P-value in t-tests, VIP-values and fold change. Significant enrichment pathways of differential metabolites were screened using KEGG enrichment analysis. [Results]  A total of 1 072 differential metabolites were identified. Among these, 674 significantly increased, and 398 significantly decreased, during diapause. These were mainly phospholipids, lysophosphatides, amino acids and their derivatives, and carbohydrates. KEGG pathway enrichment analysis indicated that there were significant changes in the synthesis and metabolism of various amino acids, and in the tricarboxylic acid cycle pathway, indicating significant changes in, and mutual transformation of, energy-storing substances that improve cold tolerance during diapause. [Conclusions]  A preliminarily investigation of metabolic differences between diapausing and non-diapausing T. dendrolimi prepupae sheds light on the metabolic regulation mechanisms and pathways regulating diapause in this species.