Two components of velocity are distinguished and measured by two closed optic-electro-hybrid-feedback loops for counting and tracking in a two-dimensional counting-tracing LDA measurement system. The effective frequencies of optical electric signals are sorted automatically into the corresponding scopes of bandwidth of signal processors

respectively at certain optical frequency shift grades. At the same time

a personal computer supervises the station of the LDA system. The two-dimensional velocities are obtained after a series of disposals of the optical electronic signal frequencies and the optical frequency shifts. In this paper

the application of a two-dimensional counting and tracking LDA measurement system in the flowing measurement of asymmetric sudden wide pipe confirms the successful development of the system.