The figure is higher than the one in four average for the rest of Scotland's prison population and campaigners said it showed there was a "desperate situation" at the Stirling jail.
Cornton Vale, Scotland's only women's jail, was at the centre of a scandal in the mid-1990s after eight women committed suicide in three years, six of whom had not been convicted. The most recent suicide was in 2012.
Last year there were 281 inmates at the prison, with 179 on long-term suicide watch programmes.
Documents released by the Scottish Government confirm 64% of those in Cornton Vale were subject to the ACT2Care Suicide Risk Management Strategy.
As well as needing regular observation by prison staff, inmates under strategy are given extra support and their behaviour assessed daily.
But campaigners claim female prisoners who need to be monitored as a suicide risk should not be in jail at all.
A spokeswoman for Women In Prison said the Scottish Prison Service was covering its own back.
"They are doing that to protect themselves as an organisation," she said. "If you look at the background of most women in prison there is a high rate of substance abuse, sexual and physical abuse and mental illnesses.
"Many are very vulnerable before going into prison, which is why they are viewed as potential risks What you have to ask is: should they be in prison if they are really that vulnerable?"
A spokesman for Prison Fellowship Scotland said: "The situation is desperate. We think most people in prison with mental illnesses should not be there.
"It's not the well educated, rich people that are in there. It illustrates how if things are bad for you then you are likely to end up in prison."
John Lamont, Scottish Conservatives' chief whip, said: "This is a worrying figure, and shows that things need to change inside our prisons. There is clearly an issue in Cornton Vale that needs looked at."
But he added: "That should not mean bowing to the demands of those who seem to think the vast majority of female offenders should not be jailed at all."
The strategy document warns women are particularly at risk, highlighting separation from children, history of sexual abuse and depression as issues.
Six of the young women who killed themselves at Cornton Vale between 1995 and 1998 were on remand. There were two further deaths during the 2000s, leading to calls for the jail's closure.
Scotland's largest jail, Barlinnie, in Glasgow, had the highest number of offenders on suicide watch, with 40% of their 1207 inmates on a care plan. But at Glenochil only 3.8% of the 650 inmates were on ACT2Care, while at HMP Shotts 4.3% of the 534 prisoners were considered at risk.
At Addiewell Prison, West Lothian, 23.2% of the 767 inmates were considered a threat to themselves, and at Kilmarnock 33% of the 577 were on ACT2Care.
The figures were released after it was revealed this week that 28 prisoners in Scotland had committed suicide in the past three years.
A spokesman for the Scottish Prison Service said its staff erred on the side of caution. He said: "Many of the women have extremely acute mental and physical needs and many would probably be better in a different environment. The numbers are high because we are trying to prevent self harming and suicide. One person self harming is one person too many."