An angular analysis and a measurement of the differential branching fraction of the decay $B^0_stophimu^+mu^-$ are presented, using data corresponding to an integrated luminosity of $3.0, {rm fb^{-1}}$ of $pp$ collisions recorded by the LHCb experiment at $sqrt{s} = 7$ and $8, {rm TeV}$. Measurements are reported as a function of $q^{2}$, the square of the dimuon invariant mass and results of the angular analysis are found to be consistent with the Standard Model. In the range $1<q^2<6, {rm GeV}^{2}/c^{4}$, where precise theoretical calculations are available, the differential branching fraction is found to be more than $3,sigma$ below the Standard Model predictions.