The temperature dependent thermoelectric power (TEP) for a series of superconducting Y(Ba 2 - x Sr x )Cu 3 O 6 . 9 5 with x=0 to 0.8 has been investigated. We have kept the oxygen content at the optimal value (6.95+/-0.02) and have changed the lattice parameters by Sr-doping to study the strain dependent TEP. We have observed that a hump occurs at 240 K for all samples except that with x=0. With increasing the Sr-doping level, S shifts to a higher value and changes its sign from negative to positive. This study demonstrates that the sign as well as the absolute value of TEP has been affected by the lattice strains.