Owing to direct band gap and strong spin-orbit coupling, monolayer transition-metal dichalcogenides (TMDs) exhibit rich new physics and great applicable potentials. The remarkable valley contrast and light emission promise such two-dimensional semiconductors a bright future of valleytronics and light-emitting diodes (LEDs). Though the electroluminescence (EL) has been observed in mechanically exfoliated small flakes of TMDs, considering real applications, a strategy which could offer mass-product and high compatibility is greatly demanded. Large-area and high quality samples prepared by chemical vapour deposition (CVD) are perfect candidates towards such goal. Here, we report the first demonstration of electrically tunable chiral EL from CVD-grown monolayer WS2 by constructing a p-i-n heterojucntion. The chirality contrast of the overall EL reaches as high as 81% and can be effectively modulated by forward current. The success of fabricating valley LEDs (vLEDs) based on CVD WS2 opens up many opportunities for developing large-scale production of unconventional 2D optoelectronic devices.