Flow in a pipe is a classic problem of engineering fluid mechanics. For this problem, coefficient of onway resistance, empirical coefficient of initial pipe length and boundary condition of velocityinlet are comprehensively discussed. Base on finite volume method, the internal flow field of laminar flow in pipe was simulated under the conditions of different Reynolds. The errors of onway resistance coefficients confirmed by simulation and theoretical calculations were discussed. The empirical coefficient of initial length of pipe before laminar flow was corrected. The influence of boundary conditions of average velocityinlet and parabolic velocityinlet on the flow field distribution of pipe flow is discussed.