The hydrodynamics and mixing during the nonaxisymmetry impingement of a micro-droplet and a sessile droplet of the same fluid are investigated by many-body dissipative particle dynamics (MDPD) simulation. In this work

the range of the impingement angle (

θ

i

) between the impinging droplet and the sessile droplet is 0°–60° and the contact angle is set as 45° or 124°. The droplets impingement and mixing behavior is analyzed based on the droplet internal flow field

the concentration distribution and the time scale of the decay of the kinetic energy of the impinging droplet. The dimensionless total mixing time (

τ

m

) is calculated by a modified mixing function. With the Weber number (

We

) ranging from 5.65 to 22.7 and the Ohnesorge number (

Oh

) ranging from 0.136 to 0.214

we find

τ

m

hardly changes with

We

and

Oh

. Whereas

θ

i

and surface wettability are found to have a significant effect on

τ

m

. We find that

θ

i

has no clear effect on

τ

m

on a hydrophobic surface

while on the hydrophilic surface

τ

m

increase with the

θ

i

. Thus

reducing the impinging angle is a valid method

to shorten the

τ

m

.