The utility model discloses a full heat recovery system of gas boiler flue gas second grade, this system by heat pipe exchanger and graphite gather the second propylene heat exchanger of perfluor, direct combustion type absorption heat pump forms. Heat pipe exchanger mainly retrieves the flue gas sensible heat as one -level heat reclamation device, the circulating water passes through heat pipe exchanger and flue gas heat transfer, and it is direct to the terminal heating of each heating to make hot water, graphite gathers the second propylene heat exchanger of perfluor and direct combustion formula heat pump is second grade heat reclamation device, mainly the latent heat of recycle -water vapour. The circulating water gathers the second propylene heat exchanger of perfluor through graphite must low temperature hot water, and rethread direct combustion type absorption heat pump unit makes high temperature hot water to the terminal heat supply of heating. Adopt the utility model discloses a full heat recovery system of gas boiler flue gas second grade can retrieve the latent heat of flue gas sensible heat and vapor, has improved gas boiler's the thermal efficiency greatly, has realized the make full use of of the energy.