Accelerated life testing (ALT) is widely used to determine the failure time distribution of a product and the associated life-stress relationship in order to predict the product's reliability under normal operating conditions. Many types of stress loadings such as constant-stress, step-stress and cyclic-stress can be utilized when conducting ALT. Extensive research has been conducted on the analysis of ALT data obtained under a specified stress loading. However, the equivalency of ALT experiments involving different stress loadings has not been investigated. In this paper, a definition is provided for the equivalency of various ALT plans involving different stress loadings. Based on this definition, general equivalent ALT plans and some special types of equivalent ALT plans are explored. For demonstration, a constant-stress ALT and a ramp-stress ALT for miniature lamps are presented and their equivalency is investigated.