Alzheimer's disease (AD) is the most ordinary kind of dementia. Identifying genes associated with AD is a new topic, and the key is to design algorithm to search AD genes. Gene order is a permutation of genes in which similar genes are ordered together. In this paper, a function is defined on gene order, and function value measures the similarity degree between a gene and its neighbors. Through the function value, the neighbors of a gene can be identified. The genes keeping as neighbor of AD gene (APOE, presenilins 1 or 2) at any stage (control, incipient, moderate, severe) are identified as the candidate of the gene associated with AD, where AD gene has been proved acting risk factor of AD. Experiment results of this paper have been proved some genes associated with AD.