In this paper, a kind of Mg, Nb co-doped multilayer piezoelectric ceramic is prepared and a non-contact accurate testing method is introduced. Using Pb(Mg1/3Nb2/3)O3- Pb(Ni1/3Nb2/3)O3- Pb(ZrTi)O3 low temperature co-fired ceramics powder and 90/10 Ag-Pb internal electrodes, the sample is prepared with tape casting processing method and low temperature co-fired technique at 960°C. Based on non-contact method, the piezoelectric constant, butterfly curve, and temperature characters are tested. Experiments show that non-contact method is more accurate for d33 testing. The effect of mechanical load on piezoelectric performance is also investigated. Under external mechanical load, switching polarization (Ps) and remnant polarization (Pr) increase respectively. Mechanical load press is also favorable to dominate the temperature rise of the piezoelectric device.