A clonal selection clustering algorithm was proposed to solve classification problem of the slope produced by the linear trend analysis. The experimental results showed that the DBI value of 065 was significantly less than the compared three algorithms. The result of vegetation change trend was in accord with the statistic data of greenbelt for everyone and green coverage percentage in Beijing from 1998 to 2011. So the proposed method had some application value and could widely apply in long time series of vegetation change trend analysis.