A novel method of minimum frequency shift keying (MSK) which based on digital signal processing (DSP) and complex bandpass processing is proposed in the article. According to the bit value of the input data, the MSK complex bandpass signal is directly produced and then is complex bandpass filtered, the real part of the complex bandpass signal is fetched to achieve the MSK modulation. The receiving signal of MSK is sampled, and then complex bandpass filtered to attain the complex bandpass signal. The complex bandpass signal and conjugate signal of its delayed version and the phase shift factor are multiplied together. According to the imaginary part of the product, the original data is recovered. The design method of complex bandpass filter is introduced also.