With the development of digital signal processing technology, digital spectrum LDA processor are very interesting. Owing to low ratio of signal to noise, limited burst continuance and wide dynamic measurement range in LDA systems, spectrum correcting methods have to be studied in order to improve the precision of LDA processor. Energy centrobaric, ratio, zoom FFT, phase difference and spectrum simulation correcting methods are used in LDA signal processing. Through carrying out simulating calculation with three kinds of Doppler signals, ratio correcting method is picked out and applied in real-time measurement, and the satisfying result is achieved.