Summary: Hydrodynamics of liquid and gaseous products in microchannel reactor for Fischer-Tropsch synthesis is considered. It is supposed, that liquid and gaseous products of the synthesis move downward in annular flow regime. A microchannel with irregular internal walls is investigated in cylindrical symmetry. In proposed numerical technique the peculiarities of coating the microchannel walls by cobalt-based catalytic particles are taken into account. System of equations of two-phase hydrodynamics is based on the generalized equations for mass flowrate and momentum of liquid film and gaseous phase. Stable numerical algorithm for calculation the thermodynamic equilibrium in gas-liquid mixtures of synthesis products is proposed. Calculation results illustrate thermophysical properties of liquid and gaseous products. In the hydrodynamics model variations along a microchannel mass fractions and thermophysical properties of liquid and gaseous products were taking into account. Principal hydrodynamical difference between a smooth microchannel and a microchannel with random roughness is explained. Hydrodynamical parameters and gradient of pressure are investigated as functions of pressure, temperature, averaged diameter of a microchannel and chain growth probability.