Abstract: Taking the lifting arm of CAT980S wheel loader as example, the stress fields in the local area of upper joint and arm cylinder joint have been calculated numerically for two different critical operating conditions. Since a new method combining the Finite Element Method (F E M) and Boundery Element Method (B E M) is adopted and the least square B E M is used, complicated boundery shape and condition are simulated efficiently. The distribution of the stress fields of local joint area is calculated and compared to the experimental results.