Three kinds of devices based on single Er-doped CdSe nanobelt (Er-CdSe NB), single CdSe NB and four CdSe NBs in parallel were constructed by hard mask assisted with 10-m tungsten wire in diameter. The photoelectronic properties of three kinds of devices were investigated. It is found that the dark currents of Er-CdSe NB and CdSe NB (four CdSe NBs in parallel) are 4x10(-10) and 1.0x10(-13)A (8.92x10(-11)A). They have high I-on/I-off ratios with 2.21x10(4) and 8.97x10(5) (4.61x10(4)), respectively. The corresponding responsivity, external quantum efficiency and detectivity of Er-CdSe NB and CdSe NB (four CdSe NBs in parallel) are 2.17x10(3), 3.87x10(5) and 2.27x10(12)A/W; 3.84, 692 and 2.9x10(11); 1.59x10(2), 2.86x10(4) and 4.96x10(11)Jones. The responsivity R and external quantum of four CdSe NBs in parallel are higher by two orders of magnitude than that of single CdSe NB device. The detectivity D* of the former is twofold higher than that of the latter. In the meantime, R, and D* of Er-CdSe NB are 10-fold higher than those of four CdSe NBs in parallel. The superior performance of the Er-CdS NB device offers an avenue to develop highly sensitive photodetector applications.