Silkworm (Bombyx mori) is a lepidopteran-holometabolic insect and a model organism having four major developmental stages including egg, larva (with five instars), pupa and adult. To understand its developmental biochemistry, we characterized the larval haemolymph metabonome from day-3 of the third instar to pre-pupa stage (the end of spinning cocoon) using 1H NMR spectroscopy together with the composition of haemolymph fatty acids using GC-FID/MS. We unambiguously assigned more than 70 metabolites, amongst which tyrosine-o-β-glucuronide, mesaconate, 1-methylhistidine, homocarnosine and picolinate were reported for the first time from the silkworm haemolymph, to the best of our knowledge. Phosphorylcholine was the most abundant silkworm haemolymph metabolite in all developmental stages with exception for the periods before the 3th and 4th molting. We also found obvious developmental dependence for the haemolymph metabonome involving multiple pathways including skin and silk protein biosyntheses, glycolysis, TCA cycle, choline metabolism together with the metabolisms of amino acids, fatty acids, purines and pyrimidines. The levels of most amino acids in haemolymph had two drastic elevations during the feeding period of the fourth-instar and pre-pupa stage. Trehalose was the major blood sugar before day-8 of the fifth instar whereas glucose became the most abundant sugar after spinning. C18:0 and its unsaturated forms (C18:1, C18:2n6, C18:n3) together with palmitic acid were abundant fatty acids in silkworm haemolymph. The developmental changes of haemolymph metabonome were associated with intakes of dietary nutrients, biosyntheses of cell membrane, skin pigments, skin and silk proteins together with energy metabolism. These findings offered essential biochemistry information in terms of the dynamic metabolic changes associated with silkworm development.