In 2007, Levstein and Maldonado computed the Terwilliger algebra of the Johnson graph $J(n,m)$ when $3m\leq n$. It is well known that the halved graphs of the incidence graph $J(n,m,m+1)$ of Johnson geometry are Johnson graphs. In this paper, we determine the Terwilliger algebra of $J(n,m,m+1)$ when $3m\leq n$, give two bases of this algebra, and calculate its dimension.