Concerns surrounding privacy leakages caused by prevalent vision-based person identifications are countless. A promising privacy-preserving solution is to identify the wireless signals reflecting persons, which, however, faces a major challenge of losing efficacy in multi-environments. In this paper, we work on person identification based on wireless signals using transfer learning, toward tackling the performance deterioration across environments. We investigate the feature variations induced by environmental shifts based on data measurements. Lay our foundation on the feature alignment concept, we propose a novel wireless-based person identification framework using transfer learning. In the framework, we integrate a series of signal processing methods including signal selection, pre-processing, and augmentation, where the first includes a reference environment to assist the feature extraction while the latter two respectively reduce the data noise and improve the data diversity. We also propose a model generalization method where a neural network is employed to align features from different environments, which facilitates the extraction of environment-independent features while incorporating both person and environment information. On a real wireless testbed consisting of an Impulse Radio Ultra-WideBand (IR-UWB) radar, we build and publicly release a dataset with 22,264 samples of ten individuals from three environments, varying in testing distance and obstruction condition. Extensive experimental evaluations demonstrate that the proposed framework can improve the identification accuracy across environments, and surpasses state-of-the-art methods by up to 18.06%.