Characteristics of silicon uptake kinetic in solution of three ratios of ammonium and nitrate were studied by modified depleting way with three different siliconefficiency rice(Teyou 998:enduring variety to silicon deficiency,Teyou 248:nonenduring variety to silicon deficiency,and BoⅡyou 15:nonsensitivity variety to silicon deficiency)treated in 0.2 mmol/L CaSO4 solution two days before being determined.The results showed that Mapping and LineweaverBurke(LB)had high veracity with 1% significant level.Silicon uptake kinetic characteristics of all treatments with three ratio of ammonium and nitrate followed the enzyme kinetic model of MichaelisMenten.Effect of carrier quantity had no distinct difference through three ratio of ammonium and nitrate,but Km or silicon affinity reached significant difference at 5% significant level.In this experimental condition,Teyou 248 had higher silicon uptake rate only at 50/50 ammonium to nitrate,and had the lowest uptake rate at 75/25 ratio,Teyou 998 had higher silicon affinity at the same condition and that may be caused by genetic essential.