The invention relates to a 2-methoxy benzene group piperazine derivative complex marked by radioactive <99m>Tc. The 2-methoxy benzene group piperazine derivative complex considers the <99m>Tc as a central core; one ligand is 2-methoxy benzene group piperazine derivative compound, the structure of which is shown in a formula (A), wherein, n is an integer of 1 to 6; carbon chain length is shown as C1 to C6; the other ligand is one kind of nitrilotriacetic acid, tris (hydroxymethyl) methyl glycine, di (hydroxymethyl) methyl glycine or hydroxyethylethylenediaminetriacetic acid. The complex can beused as 5-HT1A brain receptor imaging agent and has the advantages of simple preparation, low price, high target/non-target ratio etc. The invention also relates to a preparation method of the complex and an application of the complex as the 5-HT1A brain receptor imaging agent.