Making good use of low impedance and short wavelength characteristics of high dielectric substrate whose dielectric constant (εr) is 39 to 139, and advanced microwave integrated circuit (MIC) technology has been proposed to realize low-cost highly-reliable and small size UHF power amplifiers. Numerical calculation of single and parallel-coupled microstrip parameters on the high-dielectric constant substrate has been presented at first. Then the thick film technique application possibilities are discussed for high-dielectric substrate MICs, which is more suited for low price and mass production than conventional thin film technique. Based on theoretical and experimental estimation results, an amplifier with εr39 substrate has been developed to replace TWTs in television transposers, which provides a rated output peak power of 32 W with low distortion characteristics over the 650770 MHz frequency range. A compact 500 MHz-band 12 W class-C amplifier has also been developed successfully with use of εr139 substrate.