Using a dedicated data sample taken in 2018 on the J/Ψ peak,we perform a detailed study of the trigger efficiencies of the BESIII detector.The efficiencies are determined from three representative physics processes,namely Bhabha scattering,dimuon production and generic hadronic events with charged particles.The combined ef-ficiency of all active triggers approaches 100％in most cases,with uncertainties small enough not to affect most physics analyses.