A mixed elastohydrodynamic lubrication (mixed-EHDL) numerical model was established considering the microgroove bottom shapes of water lubricated journal bearings. The effects of different microgroove bottom shapes including semi-ellipse, rectangle, isosceles triangle, left triangle and right triangle on the mixed lubrication performance of water lubricated journal bearings were studied. The result showed that the ability to improve the mixed lubrication performance and load capacity can be ranked in the sequence of right triangle, isosceles triangle, left triangle, semi-ellipse, and rectangle. In the elastohydrodynamic lubrication stage, the microgroove bottom shapes had little influence on the friction coefficient of the water lubricated journal bearings, while in the mixed lubrication stage, with the increase of rotation speed, the effects of microgroove bottom shapes on the contact load and friction coefficient presented a regularity that it increased first, then decreased and finally tended to be uniform. In the bearing area, the right triangle bottom shapes involved a micro-step bearing effect which can significantly improve the lubrication performance, comparing to semi-ellipse, isosceles triangle, left triangle and rectangle bottom shapes.