For the first time, edge-localized mode (ELM)-free H-mode was realized in the HL-2A tokamak by using electron cyclotron resonance heating and co-current neutral beam injection (NBI) heating. This ELM-free H-mode is associated with the formation of edge particle transport barrier, an increase in density peaking and a significant decrease in edge turbulence. During the stationary ELM-free phase, an edge magnetohydrodynamic mode is identified, which has similar characteristics to an edge harmonic oscillation (EHO), as observed in other tokamaks. This EHO-like mode enhances edge particle transport, and propagates poloidally in the electron diamagnetic drift direction and toroidally in the same direction as the plasma current and NBI. A detailed analysis of this mode and the EHO–ELM transition is presented in this paper.