The produced length of whispering-gallery-mode (WGM) lasing based on polydimethylsiloxane (PDMS) is investigated. It is found that the WGM lasing has a long lasing produced length pumped by evanescent wave along the optical fiber axis. A PDMS substrate with three fiber channels is fabricated. After injecting ethanol gain solutions of rhodamine 640, rhodamine B and rhodamine 6G separately into the three channels, three-wavelength WGM lasing emission at red (628～634 nm), orange (590～597 nm) and yellow (564～572 nm) bands is successfully observed.