Ronald Reagan has never been to China but Big Bird has been there twice. Might that perchance suggest a case of twisted priorities? By now, some of the Chinese may think Big Bird is president of the United States--or at least a semi-official State Department emissary. A Muppet without portfolio.

Bird's latest trip east, "Big Bird in China," takes the form of a 90-minute NBC special produced by the Children's Television Workshop (of "Sesame Street" fame) and airing tomorrow night at 7 on Channel 4. The program's excessive length and unfortunate meditative bent may prevent it from being quite the kiddie treat that Jon Stone--executive producer, director and cowriter--imagined it would be.

But there is much to see of the country, and it has been vividly recorded on videotape. Nothing in the broadcast is quite so bluntly pretty as a sequence late in the program that finds the intreprid birdie and his pal Barkley the Dog (another larger-than-life-size Muppet) floating down the Li Jiang River. The surrounding misty hills and the glassy stillness of the water are breathtaking.

For the kids there are--kids. Cute little Chinese tots hopping around in various folk dances. Indeed, from the programs produced in China so far (including a Bob Hope special that marked B.B.'s first visit), a western viewer could get the impression that folk dancing is the major industry of the country. "Big Bird in China" shows little of city life.

Among the cutest of the children is 6-year-old Ouyang Lien-tze, selected after a talent search to be Big Bird's guide and translator. The minimal storyline has the Bird going off to find the legendary Phoenix, which eventually materializes as a twinkle of gold animation in a tree, then turns into a pretty Chinese girl, then disappears. By this time the program has become a fairly deadly reverie, one unlikely to hold a youngster's attention.

The picture of China is an emphatically benign one, as if the country were one big amusement park awaiting hordes of American tourists. Big Bird takes note of Mao's tomb in the distance, but otherwise the China of this program (a version of which will be shown on Chinese TV) is one removed from the real world.

At one point, Bird and friends are standing in front of a huge red billboard on which there is a great deal of lettering, untranslated for American viewers. Wouldn't it be funny--considering the dewy viewpoint of this production--if the sign said something like, "Death to the Yankee Imperialist Warmongers?" Oh, but I'm just too irreverent.