A non-invasive method to detect characteristic information of body tissues, wherein is the method is used to capture changes in body fluid, blood flow, and/or cardiovascular circulatory tissues, the method comprising: generating multiple synchronous alternating currents at different frequencies simultaneously with characteristics of Orthogonal Frequency Division Multiplexing symobols, OFDM symbols, by using Inverse Fast Fourier transform, IFFT, and transmitting them to a human or animal body; receiving the alternating currents modulated by tissues and their changes in the human or animal body; amplifying the modulated alternating currents and digitally converting them into digital signals; pre-processing the digital signals, the pre-processing further comprising: segmenting the digital signals into OFDM symbol sequences, demodulating the OFDM symbol sequences by using FFT to obtain frequency domain signals; and estimating a state of a target tissue based on frequency domain signals, characterised in that estimating the state of a target tissue based on the frequency domain signals comprises: separating the frequency domain signals and filtering the separated frequency domain signals; calculating the resistance and capacitance values of the target tissue and peripheral tissues; and estimating the state of the target tissue based on the resistance and capacitance values, wherein the estimating the state of the target tissue based on the resistance and capacitance values comprises: performing multi-chamber modeling based on the resistance and capacitance values, where each chamber consists of a resistor and a capacitor connected in parallel, and the multiple chambers are connected in series, or in parallel, or in a manner of combination of serial and parallel connections. generating multiple synchronous alternating currents at different frequencies simultaneously with characteristics of Orthogonal Frequency Division Multiplexing symobols, OFDM symbols, by using Inverse Fast Fourier transform, IFFT, and transmitting them to a human or animal body; receiving the alternating currents modulated by tissues and their changes in the human or animal body; amplifying the modulated alternating currents and digitally converting them into digital signals; pre-processing the digital signals, the pre-processing further comprising: segmenting the digital signals into OFDM symbol sequences, demodulating the OFDM symbol sequences by using FFT to obtain frequency domain signals; and estimating a state of a target tissue based on frequency domain signals, characterised in that estimating the state of a target tissue based on the frequency domain signals comprises: separating the frequency domain signals and filtering the separated frequency domain signals; calculating the resistance and capacitance values of the target tissue and peripheral tissues; and estimating the state of the target tissue based on the resistance and capacitance values, wherein the estimating the state of the target tissue based on the resistance and capacitance values comprises: performing multi-chamber modeling based on the resistance and capacitance values, where each chamber consists of a resistor and a capacitor connected in parallel, and the multiple chambers are connected in series, or in parallel, or in a manner of combination of serial and parallel connections. separating the frequency domain signals and filtering the separated frequency domain signals; calculating the resistance and capacitance values of the target tissue and peripheral tissues; and estimating the state of the target tissue based on the resistance and capacitance values, wherein the estimating the state of the target tissue based on the resistance and capacitance values comprises: performing multi-chamber modeling based on the resistance and capacitance values, where each chamber consists of a resistor and a capacitor connected in parallel, and the multiple chambers are connected in series, or in parallel, or in a manner of combination of serial and parallel connections.