The interest in microalgae is due to their high nutritional value, high productivity, and adaptability to be cultured under laboratory conditions, and was observed that the salinity variable has a significant influence on their growth. P. cruentum microalgae stands out for producing commercial bio actives, although limited research on its optimal growth at different salinities was made. This study evaluated the specific growth rate, and duplication rate at 35, 45, 55, 65, and 75 gL^-1. The 55 gL^-1 treatment showed the highest cell growth (50.99x105 cells mL^-1). The highest specific growth rates were in the 55 and 75 gL^-1 treatments (µ=0.167 d^-1 and 0.164 d^-1 respectively). The duplication rate was 0.03 days, except for 35 gL^-1 (0.05 days). The possibility of phased cell growth was observed, underlining the importance of salinity in P. cruentum culture for biomass production.