This paper presents a new design method for the microwave switch, which uses p-i-n diodes loaded on slotline. A single-pole single-throw (SPST) switch based on the microstrip-slotline-microstrip (M-S-M) transition with non-uniform loading structures is first designed to validate our design approach, which controls the on and off states of the switch by applying different voltages to the diodes. Then a single-pole double-throw (SPDT) switch using p-i-n diodes loaded on slotline T-junction is proposed, which achieves great high-pass response of ON-state channel and 20 dB OFF-state suppression (OSS) within dc to 4.64 GHz. To overcome the poor selectivity of two switches, transmission zeros need to be introduced to achieve band-pass response. Therefore, the slotline of the M-S-M transition is loaded with gradient length short stubs to bring in multiple transmission zeros and achieve SPST/SPDT wideband-filtering switches with ultra-wide stopband. Finally, the proposed filtering switches are fabricated and measured. The measurement results show that the SPDT filtering switch not only provides the expected band-pass response and wide stopband from 4 to 43.5 GHz of ON-state channel, but also has 22.8 dB rejection of OFF-state channel, and the 20.8 dB port-to-port isolation from dc to 43.5 GHz.