We present a microfluidic chip for fluorescent single particle measurement, featuring three-dimensional hydrodynamic focusing and an integrated self-aligned microlens which has an adjustable focal area. Microlenses are a powerful option to increase particle detection sensitivity but generally they are limited to one focal point. The newly developed self-aligned microlens with adjustable refractive index allows focusing the stimulating laser beam for different sample fluids and hence combines increased sensitivity with versatility of the optical measurement method. The three-dimensional hydrodynamic focusing provides a stream of seriatim particles in the channel, which is an important precondition for single particle measurement. With this design, fabricated in SU-8, single fluorescent particle measurement was successfully carried out.