Based on an L1 interpolation operator, a new high-order compact finite volume scheme is derived for the 2D multi-term time fractional sub-diffusion equation. It is shown that the difference scheme is unconditionally convergent and stable in $L_{\infty }$
L
∞
-norm. The convergence order is $O(\tau ^{2-\alpha }+h_{1}^{4}+h_{2}^{4})$
O
(
τ
2
−
α
+
h
1
4
+
h
2
4
)
, where τ is the temporal step size and $h_{1}$
h
1
is the spatial step size in one direction, $h_{2}$
h
2
is the spatial step size in another direction. Two numerical examples are implemented, testifying to their efficiency and confirming their convergence order.