Ternary compounds (nano-and microparticles) of AgAsSe2 and Ag3AsSe3 have been synthesized from approximately equimolar mixtures of silver nitrate, sodium metaarsenite and sodium selenosulfate with prepared by refluxing selenium powder with concentrated sodium sulfite solution under hydrothermal conditions in ethylene glycol medium. The solutions were put into a 100 mL Teflon-lined stainless steel autoclave Speedwave four BERGHOF and sealed and then heated at the temperature of 443 K during 8 hours (pH = 5-4). The products were filtered via the glass filter and washed by deionized water and absolute ethanol for several times, then dried at 353 K in a vacuum oven for at least 1 hour for analysis. The thermogravimetric (TG) and electron microprobe analysis have been carried out. The results showed that the composition of silver selenoarsenate compounds corresponded to the formulas AgAsSe2 and Ag3AsSe3. The results of SEM images and shows the typical morphologies of synthesized products in which tubular-and stick-shaped like nano-particles can be observed and their size can be estimated from 140 nm to 310 nm. The compound of AgAsSe2 and Ag3AsSe3 was constructed using X-ray phase and differential-thermal analyses. It is ascertained by X-ray powder diffraction (XRD) that the parameters of AgAsSe2 crystallized in the tetragonal space group R3m with a = 12.54 Å, c = 11.14 Å, α = 90°, β = 90°, γ = 90°, Z = 5, Ag3AsSe3 (this compound is an allotrope of β-Ag3AsSe3) crystallizes in the orthorhombic space group Pnma, a = 8.11 Å, b = 11.34 Å, c = 20.73 Å, α = 90°, β = 90°, γ = 90°, Z = 8. The results of differential thermal analysis (DTA) AgAsSe2 compound melts congruently at Tg = 683 K, Ag3AsSe3 with incongruent type of melting at Tg = 663 K was established.