Fast Finite Element (FFE) method had advantage of high precision and fast computing velocity. The online application of FFE method was significance both in theory and practice. In this paper the fast calculation of rigid plastic finite element method (RPFEM) in hot strip rolling was developed in this paper. The results of rolling force were good agreement to the measured results. The influence of element on calculating time and accuracy was discussed. The running time of one-dimension search was reduced greatly by combining Newton method with Brent method. Improved Newton method with trust region method and forced positive definite Hessian matrix method were used to reduce the convergence time. The better initial value could be obtained by improved mid-point integral Newton method. In addition, the influence of operating system, hardware and software on the calculating time was also discussed. The project of temperature FFE online calculation application in a plate mill was put forward.