Abstract: Flow instability in parallel rectangular channels is one of the important factors to affect the operation safety of the flat-plate-type fuel assembly cores.The experiment of flow oscillations in double narrow rectangular channels has been carried out in the thermo-hydraulic loop in NPIC.The results of experimental research of thermo-hydraulic parameters on characteristics of flow oscillation in double narrow rectangular channels show that:(1) With the increasing of inlet subcooling,the limit heat flux,amplitude and period of oscillation are increased;and effects of inlet subcooling on critical quality of oscillation are of ambiguity.(2) With the increasing of inlet flow velocity,the limit heat flux and amplitude of oscillation are increased;and the critical quality and period of oscillation are reduced.(3) With the increasing of system pressure,the limit heat flux and critical quality of oscillation are increased,the amplitude of oscillation is reduced;and effects of system pressure on period of oscillation are.of ambiguity.(4) Based on the stability boundary map obtained by using N_sub and N_pch,an experimental correlation of stability boundary in double narrow rectangular channels has been obtained as follows:N_pch=3.1419 N_sub+10.014.