He pipped Dasaolu (6.64s) and third-placed Theo Campbell (6.77) from Bristol & West Athletic Club.
Wales' Bridgend-born Paralympian Aled Sion Davies, 24, threw a new personal best of 14.05m in the 7.26kg shot put.
Brett Morse - who represented Great Britain in the discus in London - recorded 15.53m in the same event.
Gemili - who went under 10 seconds for the first time last summer - was a member of the Team GB squad at the London 2012 Olympics and hopes to be selected for this summer's Rio Games.
In the women's 60m, Swansea's Hannah Brier finished third in a time of 7.39s, behind winner Asha Phillip and second-placed Amy Foster.
