It is known that small quantities of surfactant additives can greatly reduce the friction factors during the flow of a heat transfer medium. The friction factors are reduced because the generation of turbulent vortices is suppressed by the formation of rod-like micelles, and the flow remains laminar in the high Reynolds number range. However, the values of heat transfer coefficients decrease during flow laminarization. The research objective is to study the heat transfer enhancement effect of micro-bubble injection. This paper presents an experimental investigation of the heat transfer and flow characteristics of an air-surfactant solution two-phase flow through a horizontal pipe. In the experiment, micro-bubble was injected through three types of porous metal. The experimental results are as follows. The flow patterns of air-surfactant solution two-phase flow depend on the size of micro-bubble. The heat transfer coefficient is promoted by micro-bubble injection, but the effect depends on the flow pattern or the size of micro-bubble.