Based on the 3-dimensional physical model of quincunx orifice baffle longitudinal flow type heat exchanger, numerical simulation was performed to study fluid flow and heat transfer in the shell side. The RNG k-e turbulent model was adopted. Air was taken as working medium. And the effects of quincunx hole opening ratio on the baffle y at 0.148, 0.18 and 0.214 respectively and Reynolds number in the range from 4000 to 12000 on the heat transfer and pressure drop of exchanger were examined. The numerical simulation results indicate that wall jets will form when fluid flows through the quincunx holes, thus the degree of fluid mixing and heat transfer will be enhanced under the action of jet entrainment and secondary flow. Mean Nusselt number of shell side Nu and flow resistance per unit shell length Δp/lz will increase with the decrease of y and L. Compared with a single segmental baffle heat exchanger under the same conditions, Nu value of the quincunx orifice baffle exchanger is increased 14.9%~52.88%, the corresponding variance ratio of Dp ranges from 152.85% to -16.62% and the comprehensive coefficients PEC between 1.03 and 1.44 in the research scope. The comprehensive heat transfer performance can be improved by increasing y or L properly.