Over the past several years the STAR experiment at RHIC has been contributing to our understanding of the proton structure. Through its instrumentation, STAR is well equipped to measure $W rightarrow u + e$ in $sqrt{s}$ = 500/510 GeV proton-proton collisions at mid-rapidity (-1.1 $le eta le $ 1.1) . The $W$ cross section ratio ($W^+/W^-$) is sensitive to unpolarized $u$, $d$, $bar{u}$, and $bar{d}$ quark distributions. At these kinematics, STAR is able to measure the quark distributions near Bjorken-$x$ values of 0.1. The RHIC runs in 2011, 2012 and 2013 at $sqrt{s}$ = 500/510 GeV saw a significant increase in delivered luminosity from previous years. This resulted in a total data sample being collected of about 352 pb$^{-1}$ of integrated luminosity. The increased statistics will lead to a higher precision measurement of the $W^+/W^-$ cross section ratio than was previously measured by STARs 2009 run, as well as allow for a measurement of its $eta$ dependence at mid-rapidity. Presented here is an update of the $W$ cross section ratio analysis from the STAR 2011, 2012 and 2013 runs.
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