Based on $(225.3\pm2.8)\times10^6$ $J/\psi$ events collected with the BESIII detector at the BEPCII collider in Beijing in 2009, the charged Lepton Flavor Violation (cLFV) process $J/\psi\to e\mu$ is studied. The upper limit of the branching fraction is measured to be $\mathcal{B}(J/\psi\to e\mu)<1.6\times10^{−7}$ at 90\% confidence level (C.L.). Compared with BESII result, the precision is improved. The sensitivity of branching fraction based on MC simulation is provided.