  We investigate the lepton flavor violation (LFV) decays, $\tau\to l\gamma$
($l=\mu, e$) and $\mu\to e\gamma$, and the newly observed muon $g-2$ anomaly in
the framwork of a squential fourth generation model with a heavy fourth
neutrino, $\nu'$. By using the recent experimental bounds, we take the
constraints of the $4\times 4$ leptonic mixing matrix element factors,
$|V_{1\nu'} V_{2\nu'}|^2$, $|V_{1\nu'} V_{3\nu'}|^2 $ and $|V_{3\nu'}
V_{2\nu'}|^2$. We find that LFV decays and $g_\mu -2$ can exclude most of the
parameter space of the 4th generation neutrino mass $m_{\nu'}$ and give
stringent constraints on the existence of the fourth generation.
