Degradable organic semiconductors have significant potential for transient and biomedical organic electronics, but there have been only a few studies on fully degradable conjugated polymers (CPs) that achieve high electrical performance. In addition, these examples are limited to p-type CPs. In this study, a series of fully degradable n-type CPs, naphthalene diimide (NDI)-based terpolymer (PNDIT2/IM-f) are developed. The incorporation of an imine linker (IM) into the CP backbone affords the capability of facile hydrolysis degradation while maintaining efficient pi-conjugations and excellent electrical properties. An additional benefit of this molecular design is the systematic tunability of the degradation characteristics and electrical performance depending on the IM content (f(IM)). At the optimal point (f(IM) = 0.45) that enables complete degradation of the polymer under acidic conditions, the resulting PNDIT2/IM-0.45 film exhibits high electron mobility (mu(e)) of 0.04 cm(2) V-1 s(-1) in organic field-effect transistors (OFETs), demonstrating excellent potential as transient OFETs. The high mu(e) value is mainly attributed to the enlarged edge-on orientations and tighter stacking of PNDIT2/IM-f crystallites as increasing f(IM). Thus, this study provides useful guidelines for the design of fully degradable n-type CPs and establishes an important correlation between the molecular structure-electronic performance-transient properties.