相关文档：uni.requestPayment(OBJECT) | uni-app官网

示例代码：

import qs from 'qs'

async aliPay(){
	const { provider } = await uni.getProvider({ service:'payment' })
	if(provider.includes('alipay')){
		uni.request({
            url:'后端接口地址',
            data:{ //传参 },
            success(res){
                let data = res.data.data
                uni.requestPayment({
                    provider: 'alipay',
                    orderInfo: qs.stringify(data), //支付宝
                    //orderInfo: data, //支付宝
                    success: function (res) {
                        console.log('success:' + JSON.stringify(res));
                    },
                    fail: function (err) {
                        console.log('fail:' + JSON.stringify(err));
                    }
                });
            }
        })
	}
}