The preparation and properties of the Pb(Fe2/3W1/3)x(Fe1/2Nb1/2)0.86–xTi0.14O3-based thick film dielectrics are described. The Calcined Pb(Fe2/3W1/3)O3 powder, instead of glass frit, is used as the flux agent to promote densification during the firing process. Firing is conducted at temperatures below 1000℃. The dissolution of Pb(Fe2/3W1/3)O3 into the starting material and the segregation of Pb(Fe2/3W1/3)O3 along the grain boundaries result in two peaks in the dielectric constant vs temperature behaviour. By controlling the amount of Pb(Fe2/3W1/3)O3 appropriately, the temperature coefficient of capacitance may be improved. The average dielectric constant of the compositions prepared range from 783 to 1639 1 at KHz. The loss factor can be reduced by adding small amounts of MnO2, and is below 2% at 1 KHz from –25℃ to +85℃. Microscopic observation and x-ray diffraction analysis have also been conducted to confirm the mechanism deduced for explaining the results.