The primary production rates of aquatic macrophytes potamogeton malaianus and ceratophyllum demersum were measured by,"light-dark bottle" oxygen methcxl.The gross primary production rates on the basis of unit fresh or dry weight for P.malatanus are 0.43-1.50mg O₂/g FWt.h(3.76-13.03mg O₂/g DWt.h),and for C.demersum 0.44-0.45mg 0₂/g FWt.h(5.12-5.27mg O₂/g DWt, h), The net production rates are 0.15-1.44mg 0₂/g FWt,h(l.31-12.51mg 0₂/g DWt.h) and 0.08-0.25mg 0₂/g FWt.h (0.93-2.95mg 0₂/g DWt.h) respectivly.Theeffects of sample weight and light intensity on the measurement of production rate were discussed.