A bstract Recently, the study of long-lived particles (LLPs) has attracted increasing attention. In this work, we analyze the full parameter space of the Type-I Two-Higgs-Doublet Model (2HDM) that allows for light long-lived scalar ( H ) and pseudoscalar ( A ) particles. When involving a light beyongd Standard Model (BSM) Higgs, the ∆ S could be the main contribution during the global fit of the oblique parameters, which is different to ∆ T being the main factor for heavy BSM Higgs cases. By imp