The invention relates to a liquid phase hydrogenation device and method. An upstream type reactor is connected in series with a downstream type reactor; n catalyst bed layers and 2n-2 hydrogen supplementation points are respectively arranged in the upstream type reactor and the downstream type reactor, and can be used for raw material oil reaction with relatively high hydrogen consumption; at least one microhole hydrogen dissolving distributor for dispersing hydrogen into micro bubbles is arranged between every two catalyst bed layers; due to the implementation of a multi-point quantitative hydrogen supplementation mode, a gas-liquid contact area can be uniformly and effectively enlarged, the reaction can be promoted, and the hydrogenation efficiency is improved. The spacing gap between the catalyst bed layers is reduced by 50 percent or above, and the aim of improving the utilization efficiency of the reactors is fulfilled.