This paper is presented for the development of the brushless DC(BLDC) motor for the spindle motor of hard disk drives(HDD). A new BLDC Motor has the use of insulated, compacted, and iron powder for the armature core material of BLDC motors. Insulated iron powder in this paper is generally called soft magnet composite(SMC). The SMC is used for the stator of the motor instead of the laminated steel core. The motor used by SMC can have the good advantages in condition of the high frequency input power and small sized motor. It gets much more high efficiency than laminated steel core at same input power. The proposed motor has a technique of speed sensorless control. Experimental results show the performance of the proposed BLDC motors for an HDD.