The invention discloses a digital dual-phase lock-in amplifier based on a DSP (Digital Signal Processor) and LabVIEW, belongs to the field of weak signal detection, and aims to solve the problem of poor detection effect on weak sinusoidal signals of known frequencies submerged in noises in existing medium and low-level dual-phase lock-in amplifiers. The digital dual-phase lock-in amplifier comprises a signal conditioning module, a DSP module and a LabVIEW software module, wherein the signal conditioning module is used for inputting tested signals into the DSP module after amplification, low-pass filtering and direct-current biasing; the DSP module is used for sampling the conditioned tested signal to obtain a tested signal sequence, generating a sinusoidal reference signal sequence and a cosine reference signal sequence having the same frequency as the tested signals, multiplying the sinusoidal reference signal sequence and the cosine reference signal sequence with the tested signal sequence respectively, and transmitting results of two multiplying operations; and the LabVIEW software module is used for receiving the results of the two multiplying operations, performing the low-pass filtering on the results to obtain stable direct-current constants, solving amplitudes and phases of the tested signals according to the direct-current constants, and displaying the amplitudes, phases and waveforms of the tested signals. The digital dual-phase lock-in amplifier is used for detecting the weak signals submerged in the noises.