Thank you for your reply, your solution give my a hint, I find another solution:
a = torch.Tensor([[1,2,3],[4,5,6],[7,8,9]])
b = torch.Tensor([[1,3,7],[2,4,8],[3,7,9],[4,5,6]])
c = torch.Tensor([[1,2,3],[2,4,8],[3,7,9],[3,5,6],[7,8,9]])
d = torch.cat((a,b,c))
print(d.shape)
d_unique = torch.unique(d, dim=0)
print(d_unique.shape)
print(d_unique)

output:
torch.Size([12, 3])
torch.Size([7, 3])
tensor([[1., 2., 3.],
        [1., 3., 7.],
        [2., 4., 8.],
        [3., 5., 6.],
        [3., 7., 9.],
        [4., 5., 6.],
        [7., 8., 9.]])