In order to improve the characteristics of flow resistance in the valveless piezoelectric pump, a micro flow tube called oval composite was presented. It’s a kind of three-way tube, of which branch tube was composed of oval nozzle/diffuser elements and converging tube was composed of traditional nozzle/diffuser elements. In the numerical simulation, the orthogonal optimization was applied to obtain parameters of the proposed tube. The minimum width of converging tube d was 150μm and the depth of the tube H was 150μm. The optimization results showed that when the pressure difference between the inlet and outlet was fixed at 50kPa, the highest coefficient of positive and negative flow resistance λ was achieved with optimization parameters of r=75μm, L=3000μm, θ = 7°, γ = 80°, a=1000μm, b=450μm. Then, the optimized composite tubes were produced though MEMS processing technology and the experiments were carried out and compared with the numerical simulations. The results showed that the experimental value was less than simulated value with pressure difference of 10～100kPa. The positive largest mass flow difference between the experiment and simulation was 12.6%, and the negative was 5.3%. When the pressure difference was 50kPa, λ was 1.83 (positive) and 1.97(negative) with difference of 7.65%