Inclusion Criteria:
1. Male or female aged 18 to 65 years subjects;
2. Meet the Diagnostic and Statistical Manual of Manual Disorders, fifth Edition(DSM-5) criteria for Generalized Anxiety Disorder;
3. Have a Hamilton Anxiety(HAMA) Rating Scale total score ≥21 points at screening and baseline;
4. Have a Hamilton Anxiety(HAMA) Rating Scale score ≥2 points on both item 1(anxious mood) and item 2(tension) at screening and baseline;
5. Have a clinical Global Impression -severity illness (CGI-S) score≥4 points at screening and baseline.
Exclusion Criteria:
1. Meet the diagnostic criteria for other psychotic disorders(defined by DSM-5, except for GAD), including major depression disorder within 6 months prior to screening , presence or history of Schizophrenia Spectrum and Other Psychotic Disorders, Bipolar and Related Disorders, Obsessive-Compulsive and related Disorders, post-traumatic stress disorder, anorexia nervosa or bulimia and personality disorder;
2. Meet the diagnostic criteria for substance or alcohol abuse (defined by DSM-5, except for nicotine or caffeine) within 6 months prior to screening;
3. Have anxious symtoms secondary to other physical illnesses or mental illnesses and anxious induced by psychoactive substance;
4. Withdrawal psychotropic drugs within 5 half-lives (at least 2 weeks for monoamine oxidase inhibitors, at least 1 month for fluoxetine, and at least 2 weeks for benzodiazepines or barbiturates) prior to randomization;
5. Have received psychosurgery or physical therapy for psychiatric illness (such as transcranial magnetic stimulation) within 3 months prior to screening;
6. Have received systematic psychotherapy or other non-drug therapies for psychiatric disorders (such as acupuncture or light therapy) within 6 weeks prior to screening;
7. Concomitant with serious and unstable illness, including cardiovascular, hepatic, renal, hematological, endocrine illness, malignant tumors and other physical illness;
8. Have a history of seizures (except for seizures caused by febrile convulsions in childhood);
9. Have a history of gastrointestinal disease or surgery known to interfere with investigation product absorption or excretion;
10. Known or suspected allergic or severe reaction to investigation product or inactive ingredients; or allergic to venlafaxine or desvenlafaxine; or allergic constitution (defined as allergic to two or more drugs or food) and unfit to participate judged by investigator;
