Abstract: This paper gives a new deterministic algorithm for the dynamic Minimum Spanning Forest (MSF) problem in the EREW PRAM model, where the goal is to maintain a MSF of a weighted graph with n vertices and m edges while supporting edge insertions and deletions. We show that one can solve the dynamic MSF problem using $O(\sqrt n)$ processors and $O(łog n)$ worst-case update time, for a total of $O(\sqrt n łog n)$ work. This improves on the work of Ferragina [IPPS 1995] which costs $O(łog n)$ worst-case update time and $O(n^2/3 łog\fracm n )$ work.