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We report CCD $V$ and $I$ time-series photometry of the globular cluster NGC6333 (M9). The technique of difference image analysis has been used, whichenables 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 highphotometric precision has resulted in the discovery of two new RRc stars, threeeclipsing binaries, seven long-term variables and one field RRab star behindthe cluster. A detailed identification chart and equatorial coordinates aregiven for all the variable stars in the field of our images of the cluster. Ourdata together with literature $V$-data obtained in 1994 and 1995 allowed us torefine considerably the periods for all RR Lyrae stars. The nature of the newvariables is discussed. We argue that variable V12 is a cluster member and anAnomalous Cepheid. Secular period variations, double mode pulsations and/or theBlazhko-like modulations in some RRc variables are addressed. Through the lightcurve Fourier decomposition of 12 RR Lyrae stars we have calculated a meanmetallicity of [Fe/H]$_{\rm ZW}$=$-1.70 \pm 0.01{\rm(statistical)} \pm0.14{\rm(systematic)}$ or [Fe/H]$_{UVES}=-1.67 \pm 0.01{\rm(statistical)} \pm0.19{\rm(systematic)}$.Absolute magnitudes, radii and masses are also estimatedfor the RR Lyrae stars.  A detailed search for SX Phe stars in the Blue Straggler region was conductedbut none were discovered. If SX Phe exist in the cluster then their amplitudesmust be smaller than the detection limit of our photometry.  The CMD has been corrected for heavy differential reddening using thedetailed extinction map of the cluster of Alonso-Garc\'ia et al. (2012). Thishas 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$7.88\pm0.30$ kpc respectively.

A detailed census of variable stars in the globular cluster NGC 6333 (M9) from CCD differential photometry