We combined an ECDL and the fluorescence detection system into a portable frequecy-stabilized laser.We installed an atomic cesium cell inside rather than outside the external diode laser cavity in order to minimize the frequency-stablized laser to palm size.In this way, we improved the mobility of the frequecy-stabilized laser. Moreover, the enhanced intensity of laser inside the external cavity increased the signal to noise ratio of the error signal for feedback control. We used Allan variance as an efficient method to quantify noise of the laser and we found the best value was 2.9954E-12 when the time integration was 90 second and the line width of laser was 200 kHz by beat frequency. This design can be exploited to lock the offset frequency of a femtosecond frequency comb laser, thus being helpful in the reaserch of CEP(carrier-envelope phase) light source.