A new electrochemiluminescence (ECL) microoptoprobe with simple structure, small sampling volume and high efficiency was developed. It was constructed by fixing the transparent gold mini-grid on the end surface of the optical fiber, and by surrounding the fiber with the counter- and reference electrodes to form a self-contained three-electrode system. The use of mini-grid electrode increased the surface area and collection efficiency, which resulted in higher ECL signal and better sensitivity. The counter electrode together with one end of the fiber formed a mini-vessel, which eliminated the need of additional container and allowed to perform ECL detection in a very small volume (about 10μl). The microoptoprobe obtained was characterized with the Ru(bpy) 3 2 + -tripropylamine system and was applied for the determination of oxalate and chlorpromazine (CPZ). Detection limits (S/N=3) were 5x10 - 7 and 1x10 - 6 moll - 1 for oxalate and CPZ, respectively. The linear range for oxalate and CPZ extended from 1x10 - 6 to 1x10 - 3 moll - 1 , and from 5x10 - 6 to 5x10 - 4 moll - 1 , respectively.