Henoch-Schönlein purpura (HSP) is a common childhood systemic vasculitis with clinical characteristics of cutaneous palpable purpura, arthralgia/arthritis, bowel angina, and hematuria/proteinuria. HSP is identified mainly based on the above presentations. Combined with pathohistological findings of leukocytoclastic vasculitis (LCV) and IgA-immune deposits in vessel walls and/or glomeruli increase the diagnostic sensitivity and specificity. However, considering the accessibility of biopsy and some patients with atypical presentations, there are still medical unmet needs in HSP diagnosis. This article reviews the diagnosis of HSP including the aspects of classification criteria, differential diagnosis, and some laboratory findings as the biomarkers with diagnostic potential.