  We constrain models of single field inflation with the pre-\textit{Planck}
CMB data. The data used here is the 9-year Wilkinson Microwave Anisotropy Probe
(\textit{WMAP}) data, South Pole Telescope (SPT) data and Atacama Cosmology
Telescope (ACT) data. By adding in running of spectral index parameter, we find
that the $\chi^2$ is improved by a factor of $\Delta \chi^2=8.44$, which
strongly indicates the preference of this parameter from current data. In
addition, we find that the running of spectral index $\alpha_s$ does not change
very much even if we switch to different pivot scales, which suggests that the
power law expansion of power spectrum is accurate enough till the 1st order
term. Furthermore, we find that the joint constraints on $r-n_{s}$ give very
tight constraints on single-field inflation models, and the models with power
law potential $\phi^{p}$ can only survive if $0.9 \lesssim p \lesssim 2.1$, so
a large class of inflation models have already been ruled out before
\textit{Planck} data. Finally, we use the $f_{NL}$ data to constrain the
non-trivial sound speed $c_s$. We find that the current constraint is dominated
by the power spectrum constraints which have some inconsistency with the
constraints from $f_{NL}$. This poses important questions of consistency
between power spectrum and bispectrum of \textit{WMAP} data.
