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We use the spectra of Pleiades and field stars from LAMOST DR2 archive tostudy how spottedness and activity vary as a function of mass at young ages. Weobtained standard TiO band strength by measuring TiO bands near 7050 $\AA$ fromLAMOST spectra (R$\approx$1800) for large sample of field GKM dwarfs with solarmetallicity. Analysis show that active dwarfs, including late G- and earlyK-type, have extra TiO absorption compare to inactive counterparts, indicatingthe presence of cool spots on their surface. Active late K- and M-dwarfs showdeeper TiO2 and shallower TiO4 compare to inactive stars at a given TiO5, whichcould be partly explained through cool spots. We estimated cool spot fractionalcoverage for 304 Pleiades candidates by modelling their TiO2 (&TiO5) bandstrength with respect to standard value. Results show that surface of largefraction of K- and M-type members have very large spot coverage ($\sim$50%). Weanalysed a correlation between spot coverage, rotation and the amplitude oflight variation, and found spot coverage on slow rotators ($R_{o}$ > 0.1)increases with decreasing Rossby Number $R_{o}$. Interestingly, we detected asaturation-like feature for spot coverage in fast rotators with a saturationlevel of 40%-50%. In addition, spot distribution in hotter fast rotators showmore symmetrical compare to slow rotators. More interestingly, we detectedlarge spot coverage in many M type members with no or little light variation.In bigger picture, these results provide important constraints for stellardynamo on these cool active stars.

Stellar activity with LAMOST. I. Spot configuration in Pleiades