The fund will back businesses with interest- and fee-free loans of up to £25,000 for six months to its customers directly hit by the riots.
At the end of the six month period, businesses can either repay the loan or transfer any outstanding amount into a traditional loan.
Chris Sullivan, chief executive of RBS and NatWest Corporate Division, said: "We want to do everything we can for businesses affected by the riots.
"These loans will help firms waiting for insurance payments or needing urgent repairs to open for business as soon as possible. I hope that other banks will also be able to help small businesses recover, our high streets are vital for local communities and the economic recovery."
Mayor of London Boris Johnson has praised RBS in the Evening Standard for 'recognising its social responsibility', saying: "The reality is that unless we help those small businesses who are the lifeblood of our high streets at a time like this, they will not survive and we will all suffer".
The Mayor has also announced a £50million regeneration fund to rebuild damaged areas and Prime Minister David Cameron has said council tax and business rates will be temporarily suspended for seriously affected premises.
Estimates of the cost of the four days of disturbances are still being compiled by insurers but it seems likely to reach £100 million, according to research by analysts Local Data Company.
More than 500 businesses suffered direct physical damage through vandalism, looting and fire with some 200 of these in Croydon, 70 in Ealing, 40 in Clapham Junction and dozens more in Tottenham, Hackney, Brixton, Woolwich, Walthamstow, Streatham, Norbury and elsewhere.
Thousands more lost trade because local town centres were closed off by police, or warnings of violence meant they chose to close early.
Although many of the businesses targeted were larger chains such as JD Sports and Carphone Warehouse, up to two thirds of the affected businesses were independents already struggling to survive testing economic conditions.
Smarta has also been urging businesses to help each other in the clean-up and recovery, teaming up with fellow business website BusinessZone.co.uk to set-up the #bizcleanup Twitter hashtag, which has received more than 500 mentions to date.
RBS and NatWest customers affected by the disturbances should speak to their Relationship Manager or call one of the following hotlines:
NatWest business hotline: 0800 158 5977
RBS business hotline: 0800 092 3087