Abstract: For ensuring the rationality of fertigation device choice of head system in micro-irrigation, experiments on the fertilizer suction performances of three hydraulic driven pumps were carried out and the analysis on the influencing factors of the inlet flow rate and the suction amount were took place. The results showed that: the inlet flow rate of the hydraulic driven pump was related with the pressure difference between the inlet and outlet, but not related with the inlet pressure. The regression models of the inlet flow rate of the three pumps were established and the curves of three pumps varied as power function, the logarithmic equation and the quadratic function, respectively. What caused this situation was the pressure difference when they began to work and the different performance when they worked in the little pressure difference. The suction amount of the hydraulic driven pump was related with the inlet discharge and the pressure difference. The pumps could work badly with a large inlet flow or a high inlet pressure. So when the pump works, the inlet flow should not be higher than the design discharge, especially at the small fertilizer proportion. Based on the analysis, the regression models of fertilizer suction amount with inlet discharge and pressure difference were established. These can be used for the calculation of the fertilizer suction amount. Meanwhile, the three pumps worked nearly accord to the fertilizer proportion, but there were difference slightly.