$Pb_{1-x}Sr_x(Mg-{1}2}W_{1}2})O_3$$</TEX> ceramics for application in the microwave frequency range were investigated by dielectric constant and X-ray diffraction measurements. The dielectric constant curves showed two concentration dependent characteristics in the $$Pb(Mg-{1}2}W_{1}2})O_3$-rich$</TEX> region. As the Sr constant further increases to x=0.3 the dielectric curve levels off. In the concentration range between x=0.4 and x=1 in which dielectric constant dependence on temperature is negligible, it decreases and Qf value increases in the microwave frequency with increasing Sr. The temperature coefficient (${ au}_{varepsilon} $) of the dielectric constant changes from the negative to positive value between x=0.9 and x=1. The dielectric constant, Qf and $ auvarepsilon$ are correlated with tolerance factor(t). From the X-ray diffraction results for $0.1{le}x{le}1$ the cell parameter is found to decrease as x increases and B-site ordering is observed in all the composition ranges.