The purpose of this study is to develop the miniaturized duplexer filter for mobile communications using high dielectric constant (${varepsilon}$r > 100, 180) ceramic resonators. Duplexer filter was ocmposed of ceramic resonators which has been developed using BNT system and SCT system, respectively. Developed duplexer filter was formed to have Tx frequency band at 836.5 (($pm$12.5)MHz and Rx frequency band at 881.5 ($pm$12.5)MHz. Insertion loss at Tx frequency band was 1.41dB and 1.46dB, insertion loss at Rx frequency band was 3.49dB and 3.65dB, respectively. Especially, duplexer filters using dielectric cermaics with ${varepsilon}$r = 180 were 8% smaller than commercially manufactured duplexer filters using dielectric ceramics with ${varepsilon}$r = 90 by murata.