  We propose a measure of nonclassical correlation $N_{\mathcal F}^{\mathcal
G}$ in terms of local Gaussian unitary operations based on square of the
fidelity $\mathcal F$ for bipartite continuous-variable systems. This quantity
is easier to calculate or estimate and is a remedy for the local ancilla
problem associated with the geometric measurement-induced nonlocality. A simple
computation formula of $N_{\mathcal F}^{\mathcal G}$ for any $(1+1)$-mode
Gaussian states is presented and an estimation of $N_{\mathcal F}^{\mathcal G}$
for any $(n+m)$-mode Gaussian states is given. For any $(1+1)$-mode Gaussian
states, $N_{\mathcal F}^{\mathcal G}$ does not increase after performing a
local Gaussian channel on the unmeasured subsystem. Comparing $N_{\mathcal
F}^{\mathcal G}(\rho_{AB})$ in scale with other quantum correlations such as
Gaussian geometric discord for two-mode symmetric squeezed thermal states
reveals that $N_{\mathcal F}^{\mathcal G}$ is much better in detecting quantum
correlations of Gaussian states.
