An earphone with tension diaphragm includes a front portion, a rear portion, a silicone gel earplug, a filtering net and a sound generating unit. As a user pushes the earphone into his ear, the diaphragm of the sound generating unit has a deformation and thus an air turbulence would be generated. This air turbulence would then cause a deformation of the tension diaphragm and this deformation would in turn eliminate the strange and unpleasant noises generated as a user pushes an earphone into his ear. Therefore, better audio signals may be achieved and a better low-frequency effect may be reached. Also, because the earphone of the present invention is water-resistant, it may be used under water. In addition, other water-resistant earphones on the market do not have such tension diaphragm.