10. If each element in set $A$ can be expressed as the product of two different numbers from 1, $2, \cdots, 9$, then the maximum number of elements in set $A$ is $\qquad$.
10.31.

From $1,2, \cdots, 9$ each time take a pair of numbers to form a product, a total of $C_{G}^{2}=$ 36 values are obtained. However, there are repetitions, the repeated cases are
$$
\begin{array}{l}
1 \times 6=2 \times 3,1 \times 8=2 \times 4,2 \times 9=3 \times 6, \\
2 \times 6=3 \times 4,3 \times 8=4 \times 6,
\end{array}
$$

a total of 5.
Therefore, the maximum number of elements in set $A$ is $C_{9}^{2}-5=31$.