how can I get the neuroscan(64ch) montage?

I can use the method read_raw_cnt() to get my raw data, but the raw data can’t plot in sensors or topo correctly because there isn’t a montage for neuroscan(64ch).

I assume you are talking about EEG data. Can you post a list of your channel names? If these are standard channels, you can use mne.channels.make_standard_montage to get a montage.