ABC is testing still another limited series. ''China Beach'' is being introduced tonight at 9 as a television movie. Actually it's a two-hour pilot, introducing the key characters who, beginning tomorrow at 10 P.M., will strive mightily in several one-hour episodes to grab the ultimate ring on the television carousel: a contract for a full-fledged weekly series in the new fall season. ''China Beach'' is a good candidate for making it. When it's bad, it's incredibly embarrassing. But then when it's good, it's terrifically on target.
In the 1970's looking back to the early 1950's, ''M*A*S*H'' gave us the Korean War as seen through the lovable capers of a great bunch of male medics. Now in the 1980's looking back to the 1960's, ''China Beach'' brings us the Vietnam War from the vantage point of several women, including a U.S.O. entertainer, a Red Cross worker and a trained nurse tending to the wounded. China Beach is an area adjacent to an American base. The crucial concept is summed up in a network press release: ''Their drama about the unsung heroism of American women in Vietnam is laced with the humor that allowed these participants to cope with bizarre realities of a conflict that soon polarized Americans at home.'' Before groaning, give the show a chance.
''China Beach'' has been created by the writer John Sacret Young (''Testament,'' ''A Rumor of War'') and William Broyles Jr., a former editor in chief of Newsweek and himself a Vietnam veteran. They have devised a rickety structure, but a good many of the sturdy personal details keep it from falling over. They have also been given an appealing and very promising cast. Dana Delany is Nurse McMurphy, the young woman from Kansas who somehow finds herself coping with the horrors of war's casualties. Nan Woods is Cherry White, a sweet innocent who has joined the Red Cross to find her missing brother. And Chloe Webb is Laurette Barber, a flashy entertainer with a heart of gold from a poor small town in Pennsylvania. Ms. Webb is listed as making a ''special guest appearance.'' Somebody had better get her back - fast.
Here is ''China Beach'' at its overly calculated worst: Dragooned into emergency nurse duty, Laurette has to tend to a horribly burned young soldier. As it happens, he has seen Laurette in her only performance at the front. Furthermore, he carries her picture in his badly singed pocket. Laurette understandably starts weeping. But that's not enough, evidently. The soldier begs her to sing his favorite song. Would you believe ''I Believe''?
And the show at its best: McMurphy snapping at a doctor on the pressures of nursing: ''You cut off their hand but you don't have to hold it. You're not the last person they see before they die.'' Or Beckett (Michael Boatman), the young black man who takes care of the dead, peering into a body bag and saying, ''Gotta be a reason why you're in there but I don't know what it is.''
In accord with current standard practice, the time and place are evoked with period songs featuring everybody from Aretha Franklin and the Four Tops to the Mamas and the Papas. Among the men regularly wandering around this peculiar but oddly believable terrain are Dr. Richard (Robert Picardo), trying to get through the mess with exaggerated efficiency, and Boonie Lanier (Brian Wimmer), a battle veteran now content to play beach lifeguard and play his harmonica.
Mr. Young, who is also the executive producer, wrote the script for this pilot. Rod Holcomb directed. Tackling the still difficult and tender subject of Vietnam, ''China Beach'' could develop into a series worth having around.