Heat transfer mechanisms of fin, plate and fluid are analyzed and the mathematical model of multi-stream plate-fin heat exchanger containing fluid phase change and cross flows between different fluids is established by finite volume method. Experimental research on heat transfer performance of airborne three-stream plate-fin condenser in four different operating conditions is conducted on the experimental evaporative cooling circulatory system. And then heat transfer characteristics between each fluid in specific operating condition are analyzed by the fluid temperature field. Besides, comparison between experimental and numerical results shows that the biggest relative error of heat exchange volume is 8.08%. It demonstrates that numerical calculation method can meet the requirements of engineering design. By qualitative analysis, the calculation errors are mainly influenced by flow un-uniform distribution, the calculation for latent heat and the surface convection heat transfer coefficient for phase change liquid.