Increase in the air pollution in past decades has driven the research towards the cleaner combustion technology for automobile engines. To tackle the challenge of the trade-off between the NOx and soot emission in conventional diesel combustion (CDC) engine, premixed low-temperature combustion (LTC) strategy is a promising approach. Among the LTC strategies, reactivity controlled compression ignition (RCCI) strategy has a better combustion phasing control along with higher fuel conversion efficiency and lower NOx and soot emissions. The present study investigates the nano-particle emissions from RCCI engine fuelled with a port injection of gasoline/methanol and direct injection of diesel. A single cylinder, water-cooled, 625cc automotive diesel engine with development ECU (electronic control unit) was modified, and a separate port fuel (PF) injector is installed in the intake manifold to operate the engine in RCCI combustion mode. The mass of injected fuel per stroke for the port as well as the direct injection is controlled through ECU. A differential mobility spectrometer (DMS) is used for the measurement of particle concentration along with their size-number distribution (particle mobility diameter range: 5nm to 1000 nm). The effect of single and double injection of high reactivity fuel on particle emission has been investigated at different engine loads for RCCI combustion vis-à-vis conventional diesel mode. The results indicate that in RCCI combustion strategy, the nucleation mode particles are in relatively higher concentration as compared to accumulation mode particles. With retard main injection timing (close to TDC) of high reactivity fuel (diesel), the particle number-size distribution curve shifts toward the bimodal lognormal distribution curve.