Figures released to MailOnline under Freedom of Information laws showed that £637,791.63 was spent through the security assistance budget of the Independent Parliamentary Standards Authority (Ipsa) since June 16.
The figure was up to date as of October 26.
Mrs Cox was set upon outside her constituency surgery in Birstall, near Leeds, in front of her staff and shocked residents on June 16.
Thomas Mair, 53, is accused of repeatedly shooting and stabbing the 41-year-old Remain campaigner a week before the EU referendum vote.
Separate statistics released by Ipsa show that it marks a huge increase on the total £160,000 spent on security for MPs in the 2015-16 financial year, which in itself was more than double the £77,000 in the previous year.
In total, MPs were paid £113.6 million for expenses and business costs by Ipsa - up from £106 million in 2014-15.
This figure does not include security spending, or the £172,600 for disability assistance.
The watchdog said the increase on the previous year could be attributed to the one-off costs of winding up MPs' offices after the 2015 general election and starting up new ones.
The money included more than £80.2 million on staffing, £11.2 million on office costs, £7.2 million on accommodation, £4.8 million on travel and £10 million on "other costs".
Ipsa's chief executive, Marcial Boo, said: "Members of Parliament do a demanding job that is important for our democracy.
"Ipsa helps them carry out their role, both in Westminster and in their constituencies, by paying their legitimate business costs within a strong regulatory framework.
"We publish all their spending, and today we show that MPs' business costs in 2015-16 were broadly the same as in the previous year, with the addition of the one-off costs of the May 2015 general election, such as the winding up of MPs' offices and paying start-up costs for new MPs.
"More than 70% of the money we spend on MPs pays the salaries of their staff. These are dedicated people who help MPs to provide a service to their constituents up and down the country. This proportion has remained largely constant from previous years.
"2015-16 also saw Ipsa's spending on MPs' security increase from £77,234.67 to £160,023.53, even before the tragic events of June. It is important that we take their security, and that of their families and their staff, very seriously.
"This year we are publishing MPs' spending on a new website to make it easier for the public to see what their own representative has spent. We are also trialling providing MPs with an opportunity to comment on their spending, should they wish to do so."
According to Ipsa, 66 MPs were granted "enhanced" security packages after the killing of Mrs Cox, indicating that police may consider they are at a greater risk.
The expenses watchdog has also approved 124 applications for "lone worker devices", which can connect users to the authorities, for MPs and staff since Mrs Cox's death.