A 5 cm fiber Bragg grating distributed feedback Bragg (DFB) fiber laser is fabricated by using 248 nm KrF excimer laser, the fiber used is regular Er-doped fiber with peak absorption of 5 dB/m, the fiber laser has a output power of 50 μW and 50 dB sidelobe suppression ratio by a 100 mW 980 nm pump laser. Coupled-mode theory was introduced to analyze DFB fiber laser output characteristics and transfer-matrix method was used to simulate a 5 cm phase shifted DFB fiber laser. From the analysis, it showed that the cavity loss is a very important factor affecting the output power, larger loss corresponds to lower grating coupling coefficient. Hence, when fabricating DFB fiber laser on regular Er-doped fiber, the cavity loss evaluation and coupling coefficient optimization could yield high output power.