We propose a new approach to obtain ultra-high piezoelectric coefficients that can be infinitely large theoretically,where ferroelectrics with strain-sensitive Curie temperature are necessary.We show the first-principles plus Monte Carlo simulation evidence that many hydrogen-bonded ferroelectrics(e.g.organic PhMDA)can be ideal candidates,which are also flexible and lead-free.Owing to the specific features of hydrogen bonding,their proton hopping barrier will drastically increase with prolonged proton transfer distance,while their hydrogen-bonded network can be easily compressed or stretched due to softness of hydrogen bonds.Their barriers as well as the Curie temperature can be approximately doubled upon a tensile strain as low as 2％.Their Curie temperature can be tuned exactly to room temperature by fixing a strain in one direction,and in another direction,an unprecedented ultra-high piezoelectric coefficient of 2058 pC/N can be obtained.This value is even underestimated and can be greatly enhanced when applying a smaller strain.Aside from sensors,they can also be utilized for converting either mechanical or thermal energies into electrical energies due to high pyroelectric coefficients.