As fundamental technical support to instantaneous E-healthcare services, Wireless Body Area Networks (WBANs) have attracted huge attention in the scientific and industrial community in recent years, which defines a unique wireless communication protocol for medical and healthcare circumstances. However, the concerns of the network and data security in WBANs have become an obstacle to the rapid development of it. In this paper, a double chaotic encryption method containing the natural randomness by adding physiological signal, electroencephalogram (EEG), is proposed. Initially, the three-dimensional eigenvalues contained deep multi-domain features are extracted as the initial factors of the chaos-based pseudo-random number generator to ensure the natural randomness of the initial values. Then, a hybrid pseudo-random number generator based on two chaotic maps, Piecewise linear Map (PLCM) and Coupled Logistic-Tent map (LTM), is proposed, which has the advantages of high randomness and low hardware complexity. Finally, the double chaotic encryption method based on the EEG eigenvalue for WBANs is presented. Various types of evaluations are performed to verify the efficiency and robustness of the proposed solution.