Polarization and strain induced by unipolar electric field (Pulcorner, Sulcorner), those induced by bipolar electric field (P, S) and remanent polarization (Pulcorner) were investigated in 0.9Pb(MgulcornerNbulcorner)O$_3$-$0.1PbTiO_3$relaxor ferroelectric ceramics in the temperature range of $-50^{circ}C$~$90^{circ}C$. From the temperature dependence of polarization and strain, the transition from predominantly paraelectric (electrostrictive) to partially ferroelectric (piezoelectric) is visualized. Under the given temperature, the Pulcorner/Pulcorner is always larger than the Sulcorner/Sulcorner and the difference between them becomes larger ass the temperature decrease. The Sulcorner/Pulcorner increases as the temperature decreased below phase transition temperature. It was suggested that these experimental results might be explained with a simple rigid ion model concentrating on BOulcorner octahedron.