Abstract: Magnetic Resonance Imaging (MRI) is a powerful method for clinical diagnosis and therapy due to the distinguishing characteristics of providing high-quality three-dimensional images of soft tissue without the need for harmful ionizing radiation. Complexes of gadolinium(Ⅲ) have proven to be especially effective MRI contrast agents, as it is estimated that they are needed for over 30% of the patients to accelerate relaxation rate of in vivo water protons, thus enhancing the contrast of different biological tissues and definition between normal tissues and diseased parts. For more sensitive small-molecule gadolinium-based MRI contrast agents, one essential requirement is to increase the hydration number q, which enhances the gadolinium's relaxivity. However, with the concern of chronic kidney disease (CKD) and nephrogenic systemic fibrosis (NSF), competition between strong chelate stability and free water coordination sites has increasingly become a challenge to MRI enhancement agent design. A highly stable N-oxide-DTPA-bisamide-based Gd(Ⅲ) complex with 3 coordinated water molecules is synthesized. The general methods such as ¹H-NMR, ¹³C-NMR and ESI-MS spectroscopy are used to characterize the structures of the ligand and the complex. The hydration number determined by the fluorescence lifetime of its Europium(Ⅲ) analogue is 3. MRI measurement shows much higher relaxivity value (16.39 mM^-1·s^-1) than commercial contrast agents. By fitting the potentiometric data with HYPERQUAD program, the formation constants of the Gd(Ⅲ) complex are calculated and demonstrated a superior stability over Gd-DTPA-BMA (Omniscan^®). Meanwhile, in vivo imaging shows good imaging quality and cell tests reveal low cytotoxicity of the complexes, which indicate its great potential for future clinical applications.