Soft materials, whose Young’s modulus typically scatters between 104 and 109 Pa, have the basic characteristic that they may strongly respond to weak stimuli. The range of soft materials is so wide: not only those traditional soft materials such as rubber and liquid crystal which have been highly industrialized, but smart soft materials represented by smart gel, EAP (electroactive polymers) and SMP (shape memory polymers), etc. The special stimuli-response properties make the latter ones have broad application prospects in many significant fields, e.g., soft robotics, soft electronics, biomedical engineering, and aerospace. Focusing on the frontiers of engineering technology, this paper firstly gives brief introductions about the material properties and preparation processes of the two kinds of traditional materials, i.e., biodegradable polyurethanes and hydrogels, with emphasis on their applications in biomedicines such as targeted drug release and tissue engineering. Then, the EAPs, represented by Ionic Polymer-Metal Composites (IPMC) and Dielectric Elastomers (DE), as well as SMPs, are highlighted by the presentation and analysis for their basic characteristics and state-of-the-art applications. Finally, the problems faced in engineering applications of soft materials are analyzed, and the trend of 4D printing technology combining soft materials with additive manufacturing is prospected.