The invention discloses a method for detecting air tightness of a component by combination of accumulated helium mass spectrum coarse leakage and fine leakage. The method comprises the steps that according to a strict degree tau Hemin, an inner cavity volume, the surface adsorption helium leakage rate and leakage detection past records of the detected component, a corresponding helium-pressing and helium pre-inflated mode is selected, the fixed or flexible scheme is selected, and a measurement leakage rate criterion of coarse leakage detection is selected; the longest detection time and a measurement leakage rate criterion of fine leakage detection are designed in a quantification mode; procedures of combination detection are carried out and comprise the steps of removing adsorption helium, determining the starting valuing time and the longest detection time of the coarse leakage detection, determining the time for starting the fine leakage accumulated detection and supplementing the requirements for detecting the bigger coarse leakage. The method has the advantages that the coarse leakage missing detection in the combination detection process can be avoided, the longest time for waiting for the detection can be prolonged within the range of the most inner cavity volume, therefore, the removal of the adsorption leakage rate can meet the requirement of the measurement leakage rate criterion of the fine leakage detection, and the combination detection of the accumulated helium mass spectrum coarse leakage and the fine leakage has more applicability and operability.