У вас установлен Python?
import pandas as pd
for i,chunk in enumerate(pd.read_csv('C:/your_path_here/main.csv', chunksize=1000000)):
chunk.to_csv('chunk{}.csv'.format(i))
или
import os
os.getcwd()
csvfile = open('C:/your_path/Book1.csv', 'r').readlines()
filename = 1
for i in range(len(csvfile)):
if i % 1000000 == 0:
open(str(filename) + '.csv', 'w+').writelines(csvfile[i:i+1000000])
filename += 1