  The basic physics and recent progresses in theoretical and particle-in-cell
(PIC) simulation studies of particle acceleration in multi-island magnetic
reconnection are briefly reviewed. Particle acceleration in multi-island
magnetic reconnection is considered a plausible mechanism for the acceleration
of energetic particles in solar flares and the solar wind. Theoretical studies
have demonstrated that such a mechanism can produce the observed power-law
energy distribution of energetic particles if the particle motion is
sufficiently randomized in the reconnection event. However, PIC simulations
seem to suggest that the first-order Fermi acceleration mechanism is unable to
produce a power-law particle energy distribution function in mildly
relativistic multi-island magnetic reconnections. On the other hand, while
simulations of highly relativistic reconnections appear to be able to produce a
power-law energy spectrum, the spectral indices obtained are generally harder
than the soft power-law spectra with indices $\sim -5$ commonly observed in the
solar wind and solar flare events. In addition, the plasma heating due to
kinetic instabilities in 3D magnetic reconnection may "thermalize" the
power-law particles, making it even more difficult for multi-island
reconnections to generate a power-law spectrum. We discuss the possible reasons
that may lead to these problems.
