Microreactors have attracted the attention of many engineers in chemical industry. since they can lie used to improve yields of various chemical reactions. To use microreactors in in industrial process, it is necessary to increase the throughput. As a strategy to increase the productivity of nucroreactors, we are studying deep microchannel reactors, which are simple in structure, and thus can be introduced at a lower capital cost. One of the concerns in the application of deep microchannel reactors is the flow maldistribution, which reduces the contact area between two fluids and thus deteriorates the performance its a reactor. It is anticipated that the major cause of low maldistribution is the nonideality in the flow conditions, which can be magnified fit a microchannel with a high aspect ratio. In the present study. the impact of nonideality fit the channel geometry tin the reaction interface was studied for a microchannel with a depth of 400 mm, which is expected to be the typical dimension for industrial-scale productions. A series of computational fluid dynamics simulation was carried out for vanous flow rates and fluid properties.The iresults showed that, in a deep microchannel reactor, the effect of nonideality in the channel geometry oat the reaction interface as rather small. This result suggests that it uniform contracting of two reactant feeds can be realizable even in deep microchannel reactors.