Abstract: Al(H₂PO4)₃ solution was used as the matrix of phosphate adhesive, the effects of curing agents (MgO, Al₂O₃, and CuO) on the curing rate, curing temperature, and curing airtightness of adhesive were studied, and the influence of MgO and CuO before and after high temperature curing on the adhesive performance was also discussed. The results show that, MgO is not suitable as the curing agent due to the high activity, resulting in the rapid reaction with Al(H₂PO4)₃ matrix; Al₂O₃ is also not suitable used as the curing agent because of the low airtightness. Uncalcined CuO as curing agent shows the advantages of moderate reaction rate and good sealing performance. When the mass ratio of Al(H₂PO4)₃ matrix to CuO is 5.0:4.5, the adhesive airtightness is 0.15 MPa (not upper limit).