We investigate observational constraints on the generalized Chaplygin gas (GCG) model as the unification of dark matter and dark energy from the latest observational data: the Union SNe Ia data, the observational Hubble data, the SDSS baryon acoustic peak and the five-year WMAP shift parameter. It is obtained that the best fit values of the GCG model parameters with their confidence level are $A_{s}=0.73^{+0.06}_{-0.06}$ ($1sigma$) $^{+0.09}_{-0.09}$ $(2sigma)$, $alpha=-0.09^{+0.15}_{-0.12}$ ($1sigma$) $^{+0.26}_{-0.19}$ $(2sigma)$. Furthermore in this model, we can see that the evolution of equation of state (EOS) for dark energy is similar to quiessence, and its current best-fit value is $w_{0de}=-0.96$ with the $1sigma$ confidence level $-0.91geq w_{0de}geq-1.00$.
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