Abstract: Under low and high P application, 4 Maize genotypes were selected to study the difference of relative biological index and relative physiologic characteristics. The main results were summarized as follows : the relative biology index , relative root system secretions index and relative active oxygen eliminated enzymes (SOD、CAT) activity were higher in P-efficiency genotypes than P-inefficiency ones, but relative MDA was lower than P-inefficiency ones. It showed that ability of P-deficiency tolerance, P-absorbed, active oxygen eliminated and self-renovated of P-efficiency genotypes was higher than that of P-inefficiency ones.