We report CCD V and I time-series photometry of the globular cluster NGC 6333 ( M9 ) .
The technique of difference image analysis has been used , which enables photometric precision better than 0.05 mag for stars brighter than V \sim 19.0 mag. , even in the crowded central regions of the cluster .
The high photometric precision has resulted in the discovery of two new RRc stars , three eclipsing binaries , seven long-term variables and one field RRab star behind the cluster .
A detailed identification chart and equatorial coordinates are given for all the variable stars in the field of our images of the cluster .
Our data together with literature V -data obtained in 1994 and 1995 allowed us to refine considerably the periods for all RR Lyrae stars .
The nature of the new variables is discussed .
We argue that variable V12 is a cluster member and an Anomalous Cepheid .
Secular period variations , double mode pulsations and/or the Blazhko-like modulations in some RRc variables are addressed .
Through the light curve Fourier decomposition of 12 RR Lyrae stars we have calculated a mean metallicity of [ Fe/H ] _ { ZW } = -1.70 \pm 0.01 { ( statistical ) } \pm 0.14 { ( systematic ) } or [ Fe/H ] _ { UVES } = -1.67 \pm 0.01 { ( statistical ) } \pm 0.19 { ( systematic ) } .
Absolute magnitudes , radii and masses are also estimated for the RR Lyrae stars .

A detailed search for SX Phe stars in the Blue Straggler region was conducted but none were discovered .
If SX Phe exist in the cluster then their amplitudes must be smaller than the detection limit of our photometry .

The CMD has been corrected for heavy differential reddening using the detailed extinction map of the cluster of Alonso-García et al .
( 2012 ) .
This has allowed us to set the mean cluster distance from two independent estimates ; from the RRab and RRc absolute magnitudes , we find 8.04 \pm 0.19 kpc and 7.88 \pm 0.30 kpc respectively .