The thermal stability and antioxidant performance of 4-tert-butylcalix[4]arene (B4) and 4-tert-butylcalix[8]arene (B8) were investigated and compared with those of 3,5-di-tert-butyl-4-hydroxytoluene (BHT). Both B4 and B8 were superior to BHT in thermal stability. In addition, B4 and B8 also showed obvious antioxidant capacity in complex lithium grease (LG). Hence, calixarenes are promising antioxidants with good thermal stability and antioxidation performance.